Stephen Robb, Henrietta McMicking, Claire Bates and Jastinder Khera
All times stated are UK
'Hold in our heart the fallen'
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That's all for this live page coverage of day one of the Gallipoli campaign centenary events. Friday's commemorations are also wrapped up in this report, and we will be back on Saturday to cover Anzac Day and Turkish memorial services.
We leave you with the words of the Rev Dr David Coulter, Chaplain General to Her Majesty's Land Forces, who opened the ceremony at the Commonwealth War Graves Commission's Helles Memorial:
"We recall the courage of those who fought and died, and we give thanks for the freedom wrought by their sacrifice.
"We pray for our respective countries represented here today, asking that we may hold in our heart the fallen in whose footsteps we stand, and that we may be faithful to their legacy."
tweets: Sun setting over Cape Helles and V Beach #Gallipoli100
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Denice Spratt emails: This is a photo of my great uncle, Claude Kidman, who was part of the New Zealand Expeditionary Force.
He served in Egypt and Gallipoli and then in France where he was awarded the military medal and bar for bravery in the field.
He was a sergeant in the Medical Corps, in the Mounted Field Ambulance serving from 1914 to 1918.
My great aunt Elsie Donald - later Kidman - served from 1915 to 1918 first as a staff nurse with the Medical Corps and then later as a sister. She was at Egypt and France and also on the hospital ships.
We Kiwis are proud of the men and women who fought for us in the First World War and all other wars and for us the 25th of April is a very emotive day and we honour all who served by attendance at the Dawn Parade.
tweets: The Prince of Wales and Prince Harry attend the French service at Morto Bay #Gallipoli100
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BBC iWonder: Exploring Gallipoli
Morto Bay
The French cemetery is at Morto Bay. The French force, mostly Senegalese, was responsible for a section of the Allied line that ran about a kilometre (0.6 miles) north of the Turkish Martyrs memorial.
Morto Bay itself was far behind the front line but was open to Turkish shelling across the Straits.
"Wounded everywhere! The killed lay in confused heaps which increased as you advanced." - French medical officer Dr Subin, based at Morto Bay, writing later.
BBC iWonder: Exploring Gallipoli
Tragedy at V beach
A century ago tomorrow, soldiers from the Royal Dublin Fusiliers, the Royal Munster Fusiliers and Royal Hampshire Regiment landed at V beach at Cape Helles.
The beach was heavily fortified. As the soldiers made for land, Turkish machine gunners opened fire and the sea ran red with blood.
Of the 700 Dubliners landing, 300 were killed and many of the rest were wounded. A British naval bombardment failed to reduce Turkish fire and a later landing attempt by the Munsters suffered 70% casualties.
The British forces eventually established a toehold on the beach.
tweets: Royal Navy Guard drawn from the Ship's Company of #HMSBulwark for commemorations at Cape #Helles #Gallipoli100
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Unwinding at war
Swimming in the sea offered a rare chance for Allied soldiers to enjoy themselves. Some braved the waves during the day, while others waited for nightfall to avoid the threat of Turkish artillery.
"We had a glorious swim after dusk. The Turk guns seldom fire after dark … the beach is just crowded — all men though."
Diary of Sergeant Cyril Lawrence, 2nd Field Company of Australian Engineers, June 1915
BBC iWonder: Exploring Gallipoli
An island hospital
Almost 58,000 sick and wounded soldiers were transported from Gallipoli to Malta, which became an island hospital for Allied troops. Malta was known as the "nurse of the Mediterranean", with 27 hospitals and more than 3,000 medical staff.
Irish president honours dead
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The President of Ireland, Michael Higgins, is also attending the Commonwealth and Ireland Service at Cape Helles.
The Royal Dublin Fusiliers and the Royal Munster Fusiliers were amongst the regiments who landed on V beach on 25 April 1915.
Shadows on the wall
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From a day offering much striking imagery, this picture captures the shadows of Prince Charles and Prince Harry at the Cape Helles memorial ahead of the Commonwealth and Ireland service there.
BBC iWonder: Exploring Gallipoli
How the Allies communicated
Communications were rudimentary at Gallipoli. Many signal lamps were lost during the landings and semaphore flags were impractical under Turkish fire.
Telegraph lines and runners were the most common method of communication. Signallers could send Morse code messages at 40 words per minute.
tweets: Prince Harry gives reading at the British Helles memorial service now #gallipoli100
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'Fears would be realised'
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From Prince Charles's address at the service: "The countless letters and diaries from Gallipoli remind us all too powerfully and vividly that the battles on this peninsula were fought and endured largely by ordinary people called upon to do extraordinary tasks.
"I'm always struck by the accounts of departing soldiers that often speak of smiles, cheers and waving caps, when we can only think that deeper down there lurked dark and foreboding fears that would be realised all too often and all too soon."
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Bringing in the big guns
The Allied landings were hampered because the naval guns on their old warships were designed to hit other vessels and weren't very effective against Turkish land targets.
Ground artillery was also unreliable. Barrages let off before soldiers went over the trenches would often end early due to fears of inaccuracy. This gave the Turkish troops time to regroup and led to the slaughter of hundreds of Australian light horsemen at the Nek.
tweets: #HMSBulwark fires a gun salute to begin and end a minute of silence to remember the fallen. #Gallipoli100
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Laying of wreaths
The Prince of Wales lays the first wreath at the Commonwealth Memorial Service followed by Turkey's President Erdogan to commemorate the Ottoman losses.
Last Post
Last Post is played at Cape Helles memorial service.
tweets: The Commonwealth and Ireland Memorial Service is now taking place at Cape #Helles. #Gallipoli100
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Royal reading
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Prince Charles was among those to deliver a reading at the memorial service at Cape Helles.
'All who served'
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At the service, Air Chief Marshal Sir Joe French says: "The monument around which we gather together today honours all who served."
Commonwealth and Ireland service
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The focus is now at the Cape Helles memorial for the Commonwealth and Ireland service.
700 lost on first day
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Members of the British army's 5th Fusiliers walk past the names of Commonwealth soldiers killed during the Gallipoli campaign.
@JohnMTinsleytweets: Today we remember Gallipoli x and especially the Lancashire Fusiliers who lost 700 men on the first morning and won 6 Victoria Crosses.
tweets: #Gallipoli100 Sniffer dog checking rifles of Royal Navy ceremonial guard.
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In pictures
For more images from today's ceremonies in Gallipoli, and events in Australia and New Zealand, click here for our picture gallery.
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Mrs M, Hornsby, Australia, emails: We are British and moved to Australia seven years ago. Our children are heavily involved in the ANZAC 'week' with school.
It is amazing how much knowledge my 8, 7 and 5 year olds have absorbed. They are fascinated by the stories and are very excited to go to the dawn service tomorrow. I wouldn't usually take my little ones to an early event, but there is no stopping them!
They honour the men and woman that fought and continue to fight today. It is wonderful to see such respect from the young children. We will never forget in this household.
tweets: Prince Charles & Prince Harry arrive at Helles #Gallipoli100
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World War One dress
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Mounted Turkish gendarmes dressed as World War One Ottoman soldiers for the 100th anniversary commemorations.
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Mark Jones went out to the region in 2008 while he was serving in the Army. He went across to Gallipoli to do a battlefield tour, they went off the beaten track .
This photo was taken from the top of a bridge:
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BBC iWonder: Exploring Gallipoli
Victoria Crosses before breakfast
The British landings at X and Y beaches at Cape Helles were lightly opposed, but the terrain and lack of co-ordination meant they didn't advance far inland.
At W beach the Lancashire Fusiliers fought a fierce action against Turkish machine gunners and submerged barbed wire, winning the beach at the cost of "six Victoria Crosses before breakfast".
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James Abbott from North Bay in Canada has written in: My grandfather left the Ottawa Valley to join the Royal Naval Air Service.
He flew a seaplane during the Gallipoli campaign and was shot down and crashed in the water.
He survived, but was shot at from land. So he filled his flight suit with whatever he could and threw it on one of the wings, hoping to draw their fire away.
A destroyer rescued him later and that was the end of his war.
tweets: British rifles. Turkish cavalry. Rich symbolism #Gallipoli100
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Janette Steel, from Dingwall, in the Highlands, writes: My grandfather, Donald Allan, was presumed dead on 12th July 1915, his third wedding anniversary.
He left a wife, two children and a third on the way. His death affected my family because my grandmother took his death so badly.
He had been a regular soldier, serving in India and South Africa but came out of the army in 1908. He said goodbye to Granny at Bridge of Allan.
I hope to go to Hamilton South church in July to lay a poppy cross at the war memorial inside the vestibule there.
tweets: 48 man guard from #HMSBulwark waiting for dignitaries. #Gallipoli100
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BBC iWonder: Explore Gallipoli
Landing at Cape Helles
The main Allied landing at Gallipoli was at Cape Helles, with a smaller Anzac force landing further north on Z beach, later called Anzac Cove.
On 25 April, 1915, some 18,000 British forces landed at five beaches around the cape - 3,000 troops at Y beach and the rest at W, X, V and S beaches. Their objective for the first day was to secure a ridge about a mile inland called Achi Baba.
Around 3,000 French troops landed at Kum Kale across the Dardanelles on the Asiatic shore. This was a feint designed to confuse the enemy.
Ceremony speeches
Turkish President Recep Tayyip Erdogan and Prince Charles gave speeches at the ceremony at the Abide monument.
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BBC iWonder: Exploring Gallipoli
War horses
Horses, mules and donkeys were taken by the Allies to Gallipoli. However, the latter two coped better with the shortage of water and steep terrain. The animals played a vital role, transporting ammunition forwards and carrying back injured men to the beaches.
Live Coverage
To watch the ceremony, click the Live Coverage tab at the top of this page.
BBC iWonder: Exploring Gallipoli
Weapons
The main weapon for Allied soldiers on the Gallipoli peninsula was the infantryman's rifle, backed up with improvised "jam-tin" bombs. Machine guns were in short supply and were less effective advancing up hills.
tweets: Erdogan has given speech. Now children's choir singing at Abide #Gallipoli100
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Remembering the Turkish sacrifice
The Turkish Martyrs' Monument at Abide commemorates the sacrifice of the 86,000 Turkish soldiers who fought and died during the Gallipoli campaign.
The tens of thousands of Turks wounded during the campaign were treated by the Ottoman Red Crescent Organisation, which worked alongside army medical units. The Red Crescent relied heavily on public donations.
The monument took six years to build and was officially opened in 1960.
'Message of peace'
"I think Canakkale is a very important place from which to give a message of peace to the whole world," Mr Erdogan says.
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tweets: Turkish cavalry, in the dress of 100 years ago. #Gallipoli100
tweets: Lest We Forget. New plaque at the entrance to Helles Memorial to mark #Gallipoli100
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'Striking reminder'
"The battle of Gallipoli is a striking reminder that the Great War was a world war," Prince Charles says, adding we should "remember with shame and profound regret" the persistence of brutal conflict and intolerance across the world.
President speaks
Turkey's President Erdogan is now addressing the assembled guests.
tweets: Turkish President Erdogan arrives at International Service at Abide. Nearly 40 countries represented #Gallipoli100
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Propaganda campaign
Gallipoli stretched the Allies' already limited resources. It became the focus for recruitment in Australia and New Zealand, because it was their first World War One campaign.
Propaganda was used to idealise Anzac soldiers, and their achievements at Gallipoli, though impressive, were inflated while disasters were minimised.
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Who fought and died?
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Soldiers from Britain, Canada, India, Australia, New Zealand, France and the French African colonies all took part. They were opposed by Turkish troops under the command of both Turkish and German officers.
Families remember
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Families from all over the world are gathering to remember those who served at Gallipoli.
More than 30,000 Australians visit the Turkish peninsula every year.
Pte Eric Smith served in the 3rd Scottish Horse, part of the 2nd Mounted Division, and landed at Suvla Bay in late August 1915.
His daughter Ailsa Siemens describes how they were 250 strong when they went out, but on their return they numbered just 18. Eric was one of the lucky survivors.
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Jayne Lamb's great-grandfather, William Percival, died at Gallipoli. In this photograph he is sitting in the middle with his son Arthur seated in front of him.
You can read more recollections from families here.
tweets: The international service starting to get underway at the Turkish memorial Abide #Gallipoli100
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Landing at Gallipoli
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After attending a reception on board HMS Bulwark in the Dardanelles strait, the group of British descendants were transported to shore by landing craft.
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BBC iWonder: Exploring Gallipoli
The Turkish point of view
Modern Turkey called the Gallipoli campaign Çanakkale Boğazi - the Battle of Canakkale. They saw it as a defining moment in achieving Turkish independence from European rivals and eventually from the Ottoman rulers.
Britain and France had promised the capital Constantinople and the Straits of the Bosphorus to the Russians if they defeated the Ottoman Turks.
With the sun glinting off the water and lush forests dotting the peninsula, it's hard to imagine the horror that engulfed Gallipoli a century ago. Over nine months, the beaches became bloodbaths as Allied forces attempted their failed invasion. The anniversary is being marked by several ceremonies to remember the thousands of victims.
Prince Charles and Prince Harry started the day on HMS Bulwark, the Royal Navy's flagship. We were on board as they met veterans and descendants of the soldiers, hearing of heroism and of the intense fighting in 1915, when many troops were gunned down even before their boats landed on the beaches.
Joining the royals at the ceremonies are the prime ministers of Australia and New Zealand, for whose countries Gallipoli marked the birth of their national consciousness, fighting in major warfare for the first time as independent nations. Leading the ceremonies: the president of Turkey, which emerged from the ashes of the Ottoman Empire under Ataturk, a brilliant Gallipoli commander. It's a campaign remembered for different reasons by all sides.
Princes Charles and Harry, joined by First Sea Lord Sir George Zambellas, have met descendants of those who served in the doomed campaign.
Roger Boissier, 84, from Armathwaite near Carlisle, was honouring his father Ernest, who was awarded the Distinguished Service Cross while a Lt Cdr at Gallipoli.
Sir James Dunbar-Nasmith, 88, from Findhorn, Moray, said his father Martin - who won a VC commanding submarine raids through the Dardanelles Strait - did not talk to him about his exploits, so he learned about his war record from school friends.
Lyn Edmonds's grandfather Pte Benjamin Hurt was a Royal Dublin Fusilier who fought at Gallipoli.
She has tried to increase knowledge of Britain and Ireland's contribution to the campaign: "I still think we have a long way to go to dispel a lot of the myths".
tweets: At Chunuk Bair, an emotional site that is permanently etched in our memories.
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Harry Biles's diary
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Former BBC foreign correspondent Peter Biles has been speaking to Victoria Derbyshire about his grandfather.
One hundred years ago today, Harry Biles of the Royal Navy Division was heading for Gallipoli on the Royal George. You can read his daily diary here.
The day before he had attended the funeral of his friend, the poet Rupert Brooke - who reportedly died of septic pneumonia - on the Greek island of Skyros.
His diary entry for 24 April 1915 reads: "Sailed from Skyros at 5.30 am for landing at the Dardanelles. Under escort. Transports formed into 3 divisions... French Hospital Ship also accompanying.
"Passed Soudan about 9.30 am. Weather bright but choppy."
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BBC iWonder: Exploring Gallipoli
Why didn’t the Allied plan work?
The Allies had failed to gather enough intelligence about the terrain and climate at Gallipoli, underestimated the Turkish forces and suffered from uninspired leadership.
The Allied forces only managed to advance a few miles inland despite showing immense bravery and losing tens of thousands of men. Gallipoli was effectively a costly sideshow.
Princes join commemorations
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The Prince of Wales and Prince Harry are representing the Commonwealth during two days of Gallipoli centenary events.
BBC iWonder: Exploring Gallipoli
Life in the trenches
There was little variety in the food rations. Corned beef and dry biscuits were a staple, supplemented with bacon, cheese and jam. Fresh water had to be shipped in from Egypt and was strictly rationed during the scorching summer.
Swarms of flies carried infection from latrines and unburied corpses to food in mess tins. Disease and dysentery were rife among soldiers.
Messages to the fallen
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Australian Prime Minister Tony Abbott reads messages left at Shrapnel Valley Cemetery for Anzac fatalities in the Gallipoli campaign.
Allied forces were unable to advance far inland due to the difficult terrain and Turkish resistance. Instead, they dug trenches in to the cliffs.
Men "lived as completely enclosed as in the lanes of a city, having their habitations along them in niches undercut in the wall, sometimes curtained by hanging blankets or waterproof sheets", wrote war correspondent Charles Bean in his book, The Story of Anzac.
'Fitting tribute'
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Connie Toth in Wellington, New Zealand, emails: A very symbolic piece of art, and a fitting tribute for the 100 year Gallipoli commemorations.
The image is taken on 24.4.15 from the diving platform behind the Museum of New Zealand Te Papa Tongerewa.
tweets: #Gallipoli100 A soldier remembered at Cape Helles today
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Princes meet Gallipoli descendants
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The Prince of Wales and Prince Harry have met relatives of veterans of the Gallipoli campaign on the flight deck of the Royal Navy's flagship HMS Bulwark in Turkey's Dardanelles straits.
The royal party met 15 descendants of veterans who had been selected to join the commemorations.
Ben Goddard, 37, was there to honour his great-grandfather Pte Alfred William Goddard, of 2nd Hampshire Regiment, who landed on V Beach on 25 April 1915. He was hit on the elbow by shrapnel 11 days later, but survived the hostilities.
Mr Goddard, from Ropley, Hampshire, knew nothing about the Gallipoli campaign until he researched his family tree and found out about his ancestor's war record.
"So many men fought and did not come back. That should be remembered, whether the campaign was a disaster or not," he said.
tweets: Lyn Edmonds who will lay a wreath at Helles later at V beach & her grandfather Pte Benjamin Hurt #Gallipoli100
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What led to the Gallipoli Campaign?
In World War One, the Allies had reached a stalemate on the Western Front by September 1914. A month later the Ottoman Empire formally joined the Central Powers, led by Germany, when it bombed Russian seaports.
Winston Churchill, then First Lord of the Admiralty, planned to knock the Ottomans out of the war by attacking the capital Constantinople.
The navy first had to force open a route along the Dardanelles by the Gallipoli peninsula. This was a total disaster. A larger land assault was devised in its stead.
tweets: The Prince of Wales meets descendants of those who fought in the #Gallipoli campaign on HMS Bulwark
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Anzac Day commemorations
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In Melbourne, 5,000 poppies have been laid in Federation Square as part of the commemorations.
Gallipoli was the first campaign Australia and New Zealand fought as independent nations.
Some 10,000 Anzacs - members of the Australian and New Zealand Army Corps - died, while 23,000 were injured, having a devastating impact on the male population of the fledgling nations.
Anzac Day is widely marked each year in both countries on 25 April, the day the Allied troops landed on the Turkish peninsular.
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@RoyalNavytweets: Lone Bugler from Royal Marines School of Music plays #LastPost to commemorate #Gallipoli100 youtu.be/xL_9HqjTpJA via @YouTube
BBC iWonder: Exploring Gallipoli
What was Gallipoli?
The Gallipoli campaign was an ambitious military operation in World War One to knock the Ottoman Empire out of the war.
The British and French-led force planned to seize the capital Constantinople (now Istanbul) by launching a land and sea assault from the Turkish Gallipoli peninsula.
They planned to advance 200 miles north east to the capital but only succeeded in establishing a tiny foothold at Gallipoli.
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What's happening today?
Prince Charles and Prince Harry are among world leaders due to attend services at the site of the battle at Cape Helles, on the Turkish peninsula.
Leaders from Australia, New Zealand and Turkey will also attend events.
Warships from what were the Allied nations will fire a salute in honour of the sailors who died, while Prince Charles and Prince Harry will lay wreaths, before meeting descendants of veterans on board the Royal Navy's flagship, HMS Bulwark.
World perspectives
Events are being held over two days by the various countries who were involved in the bloody Gallipoli campaign 100 years ago. A comparison of how it is remembered in those countries, and what it means for their citizens today, is offered by a number of BBC correspondents here.
Gallipoli in numbers
About 131,000 died in the campaign - which began in 1915 - including 86,000 Turkish troops and 45,000 Allied forces.
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Welcome to the BBC News's live page marking the 100th anniversary of the Gallipoli campaign.
A series of events will be taking place on the Turkish peninsula on Friday and Saturday to commemorate one of the bloodiest campaigns of World War One.
Live Reporting
Stephen Robb, Henrietta McMicking, Claire Bates and Jastinder Khera
All times stated are UK
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Latest Post'Hold in our heart the fallen'
That's all for this live page coverage of day one of the Gallipoli campaign centenary events. Friday's commemorations are also wrapped up in this report, and we will be back on Saturday to cover Anzac Day and Turkish memorial services.
We leave you with the words of the Rev Dr David Coulter, Chaplain General to Her Majesty's Land Forces, who opened the ceremony at the Commonwealth War Graves Commission's Helles Memorial:
"We recall the courage of those who fought and died, and we give thanks for the freedom wrought by their sacrifice.
"We pray for our respective countries represented here today, asking that we may hold in our heart the fallen in whose footsteps we stand, and that we may be faithful to their legacy."
Going down of the sun
Kate Benyon-Tinker
BBC Middle East producer
tweets: Sun setting over Cape Helles and V Beach #Gallipoli100
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Denice Spratt emails: This is a photo of my great uncle, Claude Kidman, who was part of the New Zealand Expeditionary Force.
He served in Egypt and Gallipoli and then in France where he was awarded the military medal and bar for bravery in the field.
He was a sergeant in the Medical Corps, in the Mounted Field Ambulance serving from 1914 to 1918.
My great aunt Elsie Donald - later Kidman - served from 1915 to 1918 first as a staff nurse with the Medical Corps and then later as a sister. She was at Egypt and France and also on the hospital ships.
We Kiwis are proud of the men and women who fought for us in the First World War and all other wars and for us the 25th of April is a very emotive day and we honour all who served by attendance at the Dawn Parade.
Morto Bay service
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tweets: The Prince of Wales and Prince Harry attend the French service at Morto Bay #Gallipoli100
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Morto Bay
The French cemetery is at Morto Bay. The French force, mostly Senegalese, was responsible for a section of the Allied line that ran about a kilometre (0.6 miles) north of the Turkish Martyrs memorial.
Morto Bay itself was far behind the front line but was open to Turkish shelling across the Straits.
"Wounded everywhere! The killed lay in confused heaps which increased as you advanced." - French medical officer Dr Subin, based at Morto Bay, writing later.
BBC iWonder: Exploring Gallipoli
Tragedy at V beach
A century ago tomorrow, soldiers from the Royal Dublin Fusiliers, the Royal Munster Fusiliers and Royal Hampshire Regiment landed at V beach at Cape Helles.
The beach was heavily fortified. As the soldiers made for land, Turkish machine gunners opened fire and the sea ran red with blood.
Of the 700 Dubliners landing, 300 were killed and many of the rest were wounded. A British naval bombardment failed to reduce Turkish fire and a later landing attempt by the Munsters suffered 70% casualties.
The British forces eventually established a toehold on the beach.
On to V beach
Kate Benyon-Tinker
BBC Middle East producer
tweets: Princes Charles & Harry visit the cemetery at V Beach & lay flowers at some graves #Gallipoli100
Ship's Company of HMS Bulwark
Royal Navy
tweets: Royal Navy Guard drawn from the Ship's Company of #HMSBulwark for commemorations at Cape #Helles #Gallipoli100
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Unwinding at war
Swimming in the sea offered a rare chance for Allied soldiers to enjoy themselves. Some braved the waves during the day, while others waited for nightfall to avoid the threat of Turkish artillery.
"We had a glorious swim after dusk. The Turk guns seldom fire after dark … the beach is just crowded — all men though."
Diary of Sergeant Cyril Lawrence, 2nd Field Company of Australian Engineers, June 1915
BBC iWonder: Exploring Gallipoli
An island hospital
Almost 58,000 sick and wounded soldiers were transported from Gallipoli to Malta, which became an island hospital for Allied troops. Malta was known as the "nurse of the Mediterranean", with 27 hospitals and more than 3,000 medical staff.
Irish president honours dead
The President of Ireland, Michael Higgins, is also attending the Commonwealth and Ireland Service at Cape Helles.
The Royal Dublin Fusiliers and the Royal Munster Fusiliers were amongst the regiments who landed on V beach on 25 April 1915.
Shadows on the wall
From a day offering much striking imagery, this picture captures the shadows of Prince Charles and Prince Harry at the Cape Helles memorial ahead of the Commonwealth and Ireland service there.
BBC iWonder: Exploring Gallipoli
How the Allies communicated
Communications were rudimentary at Gallipoli. Many signal lamps were lost during the landings and semaphore flags were impractical under Turkish fire.
Telegraph lines and runners were the most common method of communication. Signallers could send Morse code messages at 40 words per minute.
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Fergal Keane
BBC foreign correspondent
tweets: #Gallipoli100 Prince Harry reads from AP Herbert: tomorrow we must stagger up a hill/to man a trench/to live among the lice
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Senior Middle East producer, BBC News
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'Fears would be realised'
From Prince Charles's address at the service: "The countless letters and diaries from Gallipoli remind us all too powerfully and vividly that the battles on this peninsula were fought and endured largely by ordinary people called upon to do extraordinary tasks.
"I'm always struck by the accounts of departing soldiers that often speak of smiles, cheers and waving caps, when we can only think that deeper down there lurked dark and foreboding fears that would be realised all too often and all too soon."
BBC iWonder: Exploring Gallipoli
Bringing in the big guns
The Allied landings were hampered because the naval guns on their old warships were designed to hit other vessels and weren't very effective against Turkish land targets.
Ground artillery was also unreliable. Barrages let off before soldiers went over the trenches would often end early due to fears of inaccuracy. This gave the Turkish troops time to regroup and led to the slaughter of hundreds of Australian light horsemen at the Nek.
Guns and silence
Royal Navy
tweets: #HMSBulwark fires a gun salute to begin and end a minute of silence to remember the fallen. #Gallipoli100
Laying of wreaths
The Prince of Wales lays the first wreath at the Commonwealth Memorial Service followed by Turkey's President Erdogan to commemorate the Ottoman losses.
Last Post
Last Post is played at Cape Helles memorial service.
Gathering at Cape Helles
Royal Navy
tweets: The Commonwealth and Ireland Memorial Service is now taking place at Cape #Helles. #Gallipoli100
Royal reading
Prince Charles was among those to deliver a reading at the memorial service at Cape Helles.
'All who served'
At the service, Air Chief Marshal Sir Joe French says: "The monument around which we gather together today honours all who served."
Commonwealth and Ireland service
The focus is now at the Cape Helles memorial for the Commonwealth and Ireland service.
700 lost on first day
Members of the British army's 5th Fusiliers walk past the names of Commonwealth soldiers killed during the Gallipoli campaign.
@JohnMTinsleytweets: Today we remember Gallipoli x and especially the Lancashire Fusiliers who lost 700 men on the first morning and won 6 Victoria Crosses.
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Fergal Keane
BBC foreign correspondent
tweets: #Gallipoli100 At Cape Helles now
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Kate Benyon-Tinker
BBC Middle East producer
tweets: Sail-past of ships from all nations in front of Abide & Cape Helles #Gallipoli100
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Fergal Keane
BBC foreign correspondent
tweets: #Gallipoli100 Sniffer dog checking rifles of Royal Navy ceremonial guard.
In pictures
For more images from today's ceremonies in Gallipoli, and events in Australia and New Zealand, click here for our picture gallery.
Get Involved
Email talkingpoint@bbc.co.uk
Mrs M, Hornsby, Australia, emails: We are British and moved to Australia seven years ago. Our children are heavily involved in the ANZAC 'week' with school.
It is amazing how much knowledge my 8, 7 and 5 year olds have absorbed. They are fascinated by the stories and are very excited to go to the dawn service tomorrow. I wouldn't usually take my little ones to an early event, but there is no stopping them!
They honour the men and woman that fought and continue to fight today. It is wonderful to see such respect from the young children. We will never forget in this household.
Princes at Cape Helles
Phil Mackie
BBC News correspondent
tweets: Prince Charles & Prince Harry arrive at Helles #Gallipoli100
World War One dress
Mounted Turkish gendarmes dressed as World War One Ottoman soldiers for the 100th anniversary commemorations.
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Mark Jones went out to the region in 2008 while he was serving in the Army. He went across to Gallipoli to do a battlefield tour, they went off the beaten track .
This photo was taken from the top of a bridge:
BBC iWonder: Exploring Gallipoli
Victoria Crosses before breakfast
The British landings at X and Y beaches at Cape Helles were lightly opposed, but the terrain and lack of co-ordination meant they didn't advance far inland.
At W beach the Lancashire Fusiliers fought a fierce action against Turkish machine gunners and submerged barbed wire, winning the beach at the cost of "six Victoria Crosses before breakfast".
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James Abbott from North Bay in Canada has written in: My grandfather left the Ottawa Valley to join the Royal Naval Air Service.
He flew a seaplane during the Gallipoli campaign and was shot down and crashed in the water.
He survived, but was shot at from land. So he filled his flight suit with whatever he could and threw it on one of the wings, hoping to draw their fire away.
A destroyer rescued him later and that was the end of his war.
Turkish jets
Fergal Keane
BBC foreign correspondent
tweets: #Gallipoli100 Just watching fly past of Turkish jets and waiting for ceremony to begin at Cape Helles
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Paul Murphy emails: My grandfather - born in Dublin - served with the Dublin Fusiliers and was on board the SS River Clyde on 25.4.15.
He was wounded although I do not know whether this happened at the landing or later in the campaign.
He rarely spoke of his experience there except to say how brave the Turks were.
His opinion of Winston Churchill is better left unsaid.
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Phil Mackie
BBC News correspondent
tweets: British rifles. Turkish cavalry. Rich symbolism #Gallipoli100
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Email talkingpoint@bbc.co.uk
Janette Steel, from Dingwall, in the Highlands, writes: My grandfather, Donald Allan, was presumed dead on 12th July 1915, his third wedding anniversary.
He left a wife, two children and a third on the way. His death affected my family because my grandmother took his death so badly.
He had been a regular soldier, serving in India and South Africa but came out of the army in 1908. He said goodbye to Granny at Bridge of Allan.
I hope to go to Hamilton South church in July to lay a poppy cross at the war memorial inside the vestibule there.
Marching band
Kate Benyon-Tinker
BBC Middle East Producer
tweets: Colourful Ottoman marching band at Abide #Gallipoli100
Navy guard
Lucy Hockings
BBC News correspondent
tweets: 48 man guard from #HMSBulwark waiting for dignitaries. #Gallipoli100
BBC iWonder: Explore Gallipoli
Landing at Cape Helles
The main Allied landing at Gallipoli was at Cape Helles, with a smaller Anzac force landing further north on Z beach, later called Anzac Cove.
On 25 April, 1915, some 18,000 British forces landed at five beaches around the cape - 3,000 troops at Y beach and the rest at W, X, V and S beaches. Their objective for the first day was to secure a ridge about a mile inland called Achi Baba.
Around 3,000 French troops landed at Kum Kale across the Dardanelles on the Asiatic shore. This was a feint designed to confuse the enemy.
Ceremony speeches
Turkish President Recep Tayyip Erdogan and Prince Charles gave speeches at the ceremony at the Abide monument.
BBC iWonder: Exploring Gallipoli
War horses
Horses, mules and donkeys were taken by the Allies to Gallipoli. However, the latter two coped better with the shortage of water and steep terrain. The animals played a vital role, transporting ammunition forwards and carrying back injured men to the beaches.
Live Coverage
To watch the ceremony, click the Live Coverage tab at the top of this page.
BBC iWonder: Exploring Gallipoli
Weapons
The main weapon for Allied soldiers on the Gallipoli peninsula was the infantryman's rifle, backed up with improvised "jam-tin" bombs. Machine guns were in short supply and were less effective advancing up hills.
Tourist stalls
Claire Gibson
BBC News
tweets: Turkish tourist stalls set up in anticipation at Helles Memorial ahead of the #Gallipoli100 ceremony.
Children's choir
Kate Benyon-Tinker
BBC Middle East Producer
tweets: Erdogan has given speech. Now children's choir singing at Abide #Gallipoli100
BBC iWonder: Exploring Gallipoli
Remembering the Turkish sacrifice
The Turkish Martyrs' Monument at Abide commemorates the sacrifice of the 86,000 Turkish soldiers who fought and died during the Gallipoli campaign.
The tens of thousands of Turks wounded during the campaign were treated by the Ottoman Red Crescent Organisation, which worked alongside army medical units. The Red Crescent relied heavily on public donations.
The monument took six years to build and was officially opened in 1960.
'Message of peace'
"I think Canakkale is a very important place from which to give a message of peace to the whole world," Mr Erdogan says.
Post update
Lucy Hockings, BBC News
tweets: Turkish cavalry, in the dress of 100 years ago. #Gallipoli100
'Lest we forget'
Claire Gibson
BBC News
tweets: Lest We Forget. New plaque at the entrance to Helles Memorial to mark #Gallipoli100
'Striking reminder'
"The battle of Gallipoli is a striking reminder that the Great War was a world war," Prince Charles says, adding we should "remember with shame and profound regret" the persistence of brutal conflict and intolerance across the world.
President speaks
Turkey's President Erdogan is now addressing the assembled guests.
Spit and polish
Claire Gibson
BBC News
tweets: Last minute spit and polish at Helles Memorial ahead of this afternoon's centenary service #Gallipoli100
'Heroism and humanity'
Prince Charles begins his address to the service. "We must remember the heroism and the humanity of those on both sides," he says.
Christian prayer
A Christian prayer has now also been offered at the service.
Turkish anthem
Kate Benyon-Tinker
BBC Middle East producer
tweets: Turkish national anthem played at Abide #Gallipoli100
Offering a prayer
Turkey's head of religious affairs, Mehmet Gormez, is now offering a prayer in Turkish.
Verses from the Koran
A recitation of verses from the Koran followed the laying of the wreaths.
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Kate Benyon-Tinker
BBC Middle East producer
tweets: Now the Prince of Wales also lays a wreath at the Abide memorial #Gallipoli100
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Kate Benyon-Tinker
BBC Middle East producer
tweets: #Turkey's President Erdogan lays a wreath at the Turkish memorial at Abide #Gallipoli100
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Kate Benyon-Tinker
BBC Middle East producer
tweets: Turkish President Erdogan arrives at International Service at Abide. Nearly 40 countries represented #Gallipoli100
BBC iWonder: Exploring Gallipoli
Propaganda campaign
Gallipoli stretched the Allies' already limited resources. It became the focus for recruitment in Australia and New Zealand, because it was their first World War One campaign.
Propaganda was used to idealise Anzac soldiers, and their achievements at Gallipoli, though impressive, were inflated while disasters were minimised.
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Phil Mackie
BBC News correspondent
tweets: Security cordon now around Helles #Gallipoli100
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Who fought and died?
Soldiers from Britain, Canada, India, Australia, New Zealand, France and the French African colonies all took part. They were opposed by Turkish troops under the command of both Turkish and German officers.
Families remember
Families from all over the world are gathering to remember those who served at Gallipoli.
More than 30,000 Australians visit the Turkish peninsula every year.
Pte Eric Smith served in the 3rd Scottish Horse, part of the 2nd Mounted Division, and landed at Suvla Bay in late August 1915.
His daughter Ailsa Siemens describes how they were 250 strong when they went out, but on their return they numbered just 18. Eric was one of the lucky survivors.
Jayne Lamb's great-grandfather, William Percival, died at Gallipoli. In this photograph he is sitting in the middle with his son Arthur seated in front of him.
You can read more recollections from families here.
International ceremony
Kate Benyon-Tinker
BBC Middle East producer
tweets: The international service starting to get underway at the Turkish memorial Abide #Gallipoli100
Landing at Gallipoli
After attending a reception on board HMS Bulwark in the Dardanelles strait, the group of British descendants were transported to shore by landing craft.
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The Turkish point of view
Modern Turkey called the Gallipoli campaign Çanakkale Boğazi - the Battle of Canakkale. They saw it as a defining moment in achieving Turkish independence from European rivals and eventually from the Ottoman rulers.
Britain and France had promised the capital Constantinople and the Straits of the Bosphorus to the Russians if they defeated the Ottoman Turks.
'Hard to imagine'
Mark Lowen
BBC Turkey correspondent
With the sun glinting off the water and lush forests dotting the peninsula, it's hard to imagine the horror that engulfed Gallipoli a century ago. Over nine months, the beaches became bloodbaths as Allied forces attempted their failed invasion. The anniversary is being marked by several ceremonies to remember the thousands of victims.
Prince Charles and Prince Harry started the day on HMS Bulwark, the Royal Navy's flagship. We were on board as they met veterans and descendants of the soldiers, hearing of heroism and of the intense fighting in 1915, when many troops were gunned down even before their boats landed on the beaches.
Joining the royals at the ceremonies are the prime ministers of Australia and New Zealand, for whose countries Gallipoli marked the birth of their national consciousness, fighting in major warfare for the first time as independent nations. Leading the ceremonies: the president of Turkey, which emerged from the ashes of the Ottoman Empire under Ataturk, a brilliant Gallipoli commander. It's a campaign remembered for different reasons by all sides.
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Phil Mackie
BBC News correspondent
tweets: Final rehearsals at Helles #Gallipoli100
British descendants attend events
Princes Charles and Harry, joined by First Sea Lord Sir George Zambellas, have met descendants of those who served in the doomed campaign.
Roger Boissier, 84, from Armathwaite near Carlisle, was honouring his father Ernest, who was awarded the Distinguished Service Cross while a Lt Cdr at Gallipoli.
Sir James Dunbar-Nasmith, 88, from Findhorn, Moray, said his father Martin - who won a VC commanding submarine raids through the Dardanelles Strait - did not talk to him about his exploits, so he learned about his war record from school friends.
Lyn Edmonds's grandfather Pte Benjamin Hurt was a Royal Dublin Fusilier who fought at Gallipoli.
She has tried to increase knowledge of Britain and Ireland's contribution to the campaign: "I still think we have a long way to go to dispel a lot of the myths".
Eve of Anzac Day
Tony Abbott
Prime Minister of Australia
tweets: Thank you to the Capt & crew of HMAS ANZAC for hosting me on the eve of #ANZACDAY #ANZAC100
'Etched in our memories'
John Key
New Zealand prime minister
tweets: At Chunuk Bair, an emotional site that is permanently etched in our memories.
Harry Biles's diary
Former BBC foreign correspondent Peter Biles has been speaking to Victoria Derbyshire about his grandfather.
One hundred years ago today, Harry Biles of the Royal Navy Division was heading for Gallipoli on the Royal George. You can read his daily diary here.
The day before he had attended the funeral of his friend, the poet Rupert Brooke - who reportedly died of septic pneumonia - on the Greek island of Skyros.
His diary entry for 24 April 1915 reads: "Sailed from Skyros at 5.30 am for landing at the Dardanelles. Under escort. Transports formed into 3 divisions... French Hospital Ship also accompanying.
"Passed Soudan about 9.30 am. Weather bright but choppy."
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Why didn’t the Allied plan work?
The Allies had failed to gather enough intelligence about the terrain and climate at Gallipoli, underestimated the Turkish forces and suffered from uninspired leadership.
The Allied forces only managed to advance a few miles inland despite showing immense bravery and losing tens of thousands of men. Gallipoli was effectively a costly sideshow.
Princes join commemorations
The Prince of Wales and Prince Harry are representing the Commonwealth during two days of Gallipoli centenary events.
BBC iWonder: Exploring Gallipoli
Life in the trenches
There was little variety in the food rations. Corned beef and dry biscuits were a staple, supplemented with bacon, cheese and jam. Fresh water had to be shipped in from Egypt and was strictly rationed during the scorching summer.
Swarms of flies carried infection from latrines and unburied corpses to food in mess tins. Disease and dysentery were rife among soldiers.
Messages to the fallen
Australian Prime Minister Tony Abbott reads messages left at Shrapnel Valley Cemetery for Anzac fatalities in the Gallipoli campaign.
Views from a drone
BBC Trending
tweets: #Gallipoli100: Check out this drone video of the WWI battlefield https://www.youtube.com/watch?v=GiysBodQYgg&feature=youtu.be
BBC iWonder: Exploring Gallipoli
What was Gallipoli like?
Allied forces were unable to advance far inland due to the difficult terrain and Turkish resistance. Instead, they dug trenches in to the cliffs.
Men "lived as completely enclosed as in the lanes of a city, having their habitations along them in niches undercut in the wall, sometimes curtained by hanging blankets or waterproof sheets", wrote war correspondent Charles Bean in his book, The Story of Anzac.
'Fitting tribute'
Email talkingpoint@bbc.co.uk
Connie Toth in Wellington, New Zealand, emails: A very symbolic piece of art, and a fitting tribute for the 100 year Gallipoli commemorations.
The image is taken on 24.4.15 from the diving platform behind the Museum of New Zealand Te Papa Tongerewa.
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Fergal Keane
BBC foreign correspondent
tweets: #Gallipoli100 A soldier remembered at Cape Helles today
Princes meet Gallipoli descendants
The Prince of Wales and Prince Harry have met relatives of veterans of the Gallipoli campaign on the flight deck of the Royal Navy's flagship HMS Bulwark in Turkey's Dardanelles straits.
The royal party met 15 descendants of veterans who had been selected to join the commemorations.
Ben Goddard, 37, was there to honour his great-grandfather Pte Alfred William Goddard, of 2nd Hampshire Regiment, who landed on V Beach on 25 April 1915. He was hit on the elbow by shrapnel 11 days later, but survived the hostilities.
Mr Goddard, from Ropley, Hampshire, knew nothing about the Gallipoli campaign until he researched his family tree and found out about his ancestor's war record.
"So many men fought and did not come back. That should be remembered, whether the campaign was a disaster or not," he said.
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Mark Lowen
BBC Turkey correspondent
tweets: #PrinceCharles stopping on #HMSBulwark, meeting descendants of #Gallipoli before giving readings at memorials
'A sacred place'
Lucy Hockings
BBC News correspondent
tweets: NZ PM @johnkeypm lays a poppy on the grave of a 17yr old soldier at Chunuk Bair. "A sacred place" #Gallipoli100
BBC iWonder: Exploring Gallipoli
Find your own war story
Nearly one million men from across the globe fought at Gallipoli, while 17 million took part in World War One as a whole.
Photos, cap badges and war diaries can all help you to build up a picture of what your own relations did during the conflict.
Stories of death and heroism
Mark Lowen
BBC Turkey correspondent
tweets: #PrinceHarry meeting descendants of #Gallipoli on #HMSBulwark. Hearing stories of death and heroism
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Phil Mackie
BBC News correspondent
tweets: Lyn Edmonds who will lay a wreath at Helles later at V beach & her grandfather Pte Benjamin Hurt #Gallipoli100
BBC iWonder: Exploring Gallipoli
What led to the Gallipoli Campaign?
In World War One, the Allies had reached a stalemate on the Western Front by September 1914. A month later the Ottoman Empire formally joined the Central Powers, led by Germany, when it bombed Russian seaports.
Winston Churchill, then First Lord of the Admiralty, planned to knock the Ottomans out of the war by attacking the capital Constantinople.
The navy first had to force open a route along the Dardanelles by the Gallipoli peninsula. This was a total disaster. A larger land assault was devised in its stead.
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John Key
New Zealand prime minister
tweets: Breathtaking to see Quinn's Post up close, a phenomenal story of Anzac and Turkish bravery.
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John Key
New Zealand prime minister
tweets: Visiting Lone Pine with Gallipoli historian Christopher Pugsley.
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Kensington Palace
tweets: Prince Harry is meeting descendants of those who fought in the #Gallipoli campaign on HMS Bulwark
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Mark Lowen
BBC Turkey correspondent
tweets: Nearby, #Ataturk's boat, today used by #Turkey's President #Erdogan to receive foreign dignitaries #Gallipoli100
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Clarence House
tweets: The Prince of Wales meets descendants of those who fought in the #Gallipoli campaign on HMS Bulwark
Anzac Day commemorations
In Melbourne, 5,000 poppies have been laid in Federation Square as part of the commemorations.
Gallipoli was the first campaign Australia and New Zealand fought as independent nations.
Some 10,000 Anzacs - members of the Australian and New Zealand Army Corps - died, while 23,000 were injured, having a devastating impact on the male population of the fledgling nations.
Anzac Day is widely marked each year in both countries on 25 April, the day the Allied troops landed on the Turkish peninsular.
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Royal Navy
@RoyalNavytweets: Lone Bugler from Royal Marines School of Music plays #LastPost to commemorate #Gallipoli100 youtu.be/xL_9HqjTpJA via @YouTube
BBC iWonder: Exploring Gallipoli
What was Gallipoli?
The Gallipoli campaign was an ambitious military operation in World War One to knock the Ottoman Empire out of the war.
The British and French-led force planned to seize the capital Constantinople (now Istanbul) by launching a land and sea assault from the Turkish Gallipoli peninsula.
They planned to advance 200 miles north east to the capital but only succeeded in establishing a tiny foothold at Gallipoli.
On deployment soon
Mark Lowen
BBC Turkey correspondent
tweets: #HMSBulwark in sight, here for #Gallipoli100, soon sent off for migrant rescue operations in Mediterranean
What's happening today?
Prince Charles and Prince Harry are among world leaders due to attend services at the site of the battle at Cape Helles, on the Turkish peninsula.
Leaders from Australia, New Zealand and Turkey will also attend events.
Warships from what were the Allied nations will fire a salute in honour of the sailors who died, while Prince Charles and Prince Harry will lay wreaths, before meeting descendants of veterans on board the Royal Navy's flagship, HMS Bulwark.
World perspectives
Events are being held over two days by the various countries who were involved in the bloody Gallipoli campaign 100 years ago. A comparison of how it is remembered in those countries, and what it means for their citizens today, is offered by a number of BBC correspondents here.
Gallipoli in numbers
About 131,000 died in the campaign - which began in 1915 - including 86,000 Turkish troops and 45,000 Allied forces.
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Welcome to the BBC News's live page marking the 100th anniversary of the Gallipoli campaign.
A series of events will be taking place on the Turkish peninsula on Friday and Saturday to commemorate one of the bloodiest campaigns of World War One.