Two dogs that fell 50ft from the top of Derry's walls had their lives saved after they were rushed across the border for emergency treatment by Ireland's leading animal surgeon.

Dublin vet Billy McCartney performed revolutionary surgery on the labradors, giving them bionic legs. Without the operations, which lasted 10 hours, the dogs would have been put down.

But their owners, Phil Gowdy and Carol Halliday, who work as cleaners in an east Belfast school, are now struggling to meet a €12,000 bill for the treatment. The dogs, Harvey and Katie, fell off the walls while on a walk.

They needed five operations to rebuild their toes, paws, and ankles and Harvey's dislocated hip. The Malahide-based vet had to order special titanium plates from Switzerland which cost almost €4,000.

Gowdy (41) said the freak accident which almost killed his labradors still left him unable to sleep at night. "Carol and I were walking in the sunshine, enjoying our trip to Derry, when suddenly Harvey started running and jumped over the wall. Katie followed him.

"It was a huge drop to the grass. Carol was screaming, 'Oh my God, they're dead!' When I got down, they were just lying there conscious but in terrible pain. They weren't moving. Their legs were broken and Katie had fallen on Harvey, dislocating his hip. I was so shocked, I couldn't speak."

A local woman rang the PSNI but, Gowdy said, she mistakenly told police that two children had fallen from the walls so they arrived in minutes.

"The police probably were a bit miffed when they realised it was dogs that had fallen but when they saw our distress they were brilliant." As the PSNI drove the dogs to a local vet, the police car was stoned by youths.

The dogs were later moved to Cedar Grove Vet Clinic in Belfast and then to Billy McCartney in Dublin. "We were told the treatment would be expensive but there was no way we would have our dogs put down.

"We have no children – Harvey and Katie are our kids. They're brother and sister – we got them when they were pups eight years ago. They're spoilt rotten. They have the run of the house."

Gowdy had cancelled the pet insurance just two months before the accident because he couldn't afford the €100 monthly premiums. "Now we're facing a €12,000 bill but our neighbours in east Belfast, who all love Harvey and Katie, have already raised over €1,000 for us."

After finishing his day job, Gowdy now taxis at night to earn more money. "I'll do as many night shifts as I can. I'd sell the house for Harvey and Katie. They're recovering well.

"The hardest thing is that the rehabilitation programme means they're not allowed to move. They're penned in the kitchen all day and they don't like it one bit."

Anyone wishing to contribute to the dogs' treatment can contact the Marie Louise Veterinary Hospital, 38 Warrenhouse Road, Baldoyle, Dublin 13.