An ordinary mirror is not suitable

Daniel Mills, a lecturer in behavioural studies and animal welfare, said: "Weaving is generally agreed to be a sign of stress and frustration.

"Horses are sometimes treated like cars kept in a garage but they shouldn't be kept in social isolation.

"There can often be unseen welfare problems with horses as they are owned by people who love them - but well-meaning is not always the same as well-being."

The five-week study found the mirror treatment to be effective with all the horses involved in the research.

They had all had a history of weaving for at least two years.

Stable design

The effect of the mirror lasted the length of the study and when the mirrors were removed the horses did not immediately resume the old behaviour.

But Mr Mills warned horse owners against introducing an ordinary mirror into their stables.

"A horse could simply smash it.

"We are looking to develop the shatterproof mirrors we used in the study as a commercial product."

It is hoped that further research will look at a radical redesign of all aspects of the way horses are stabled.