RSPCA inspectors are still hunting for clues to help them find who was responsible for dumping a mutilated dead mare and her foal in a field in Letchmore Heath.

Dog walkers discovered their bodies early last Thursday morning while using a public footpath through Hilfield Farm, just off Aldenham Road.

The mare was found lying in the field with one of her legs tied with a rope, pulled taught, to a tree, with her newborn foal lying underneath her body.

Mr Mark Martin, an inspector for the Hertfordshire branch of the RSPCA, said its vet believed they had both been dead for at least five days.

He has been trying to decide how the two ended up there.

On Thursday, standing next to the grisly scene, he outlined his theory so far.

The brown and white, skewbald, horse, aged about three, he said, appeared to have had difficulty giving birth and the foal became stuck. Someone then seemed to have tried to extract it by tying ropes to its feet and pulling it with a truck, ripping the mother's vulva open, which killed her.

He believed her female foal died during the procedure.

When the foal was removed from under its mother one of its legs was missing.

It then seems they were both dragged and hoisted into a truck and driven to the village.

One of the posts attached to the locked gate at the entrance to the open access field was lifted out and those responsible seem to have tied a rope to the mare's leg and the other end to a tree before driving the truck away so her body would drop to the ground in a secluded spot.

'It's beyond reason,' said Mr Martin, who in his nine years as an inspector had not come across a similar case. 'To put the horses thorugh that sort of pain and suffering is just dreadful. It's a very disturbing sequence of events.'

He said the mother was not a racing horse, was too young to be used for breeding, but may have been kept for a child, or used as a pony and trap - the latter of which he felt was more likely.

This breed, he said, are rarely given a permanent identity tag and horses do not need a licence, so tracing their owners is very difficult.

'I don't think it's someone local because people don't tend to leave their problems on their own doorstep,' he said.

If caught, those responsible could face a £5,000 fine or six-month custodial sentence.

Mr Martin urged anyone finding themselves in difficulties with a horse giving birth, who cannot afford to call out a vet, to contact the RSPCA, which can offer help free of charge.

He appealed for anyone who knows anything about the deaths to call the RSPCA's national office on 08705 555999.

'We want to stop these people from subjecting another horse to this sort of cruelty again,' he added.