Owners of a Bushey field where one horse drowned and three others had to be rescued from a deep pool of water say the animals were being kept illegally on the land.

The Woodland Trust this afternoon confirmed the animals were owned by travellers who had left them at the Merry Hill Road site without the charity’s knowledge.

Dog-walkers discovered the severely distressed animals at about 8.40am today after they had become stuck in a deep, three metre-wide pool created by a burst underground pipe.

One horse died and three of the horses were rescued by firefighters who said the animals had probably been fighting to escape the muddy well through most of the night.

Louise Neicho, Woodland Trust site manager, said: "The incident at Merry Hill is deeply distressing for all concerned. We pride ourselves on managing our sites for the benefit of both people and wildlife.

“As soon as the Trust was informed about the burst pipe we contacted the relevant water company to deal with the incident. At the time to the best of our knowledge there were no horses on site. It appears that in the intervening period, the horses, which had previously been on site, returned and the incident occurred.

“The horses in question are owned by travellers and whilst this does not mitigate the loss of life, we feel it pertinent to point out that these horses should not have been on the land and there was nothing we could have done to prevent them entering the waterlogged area."