A Belsize park man has warned fellow dog-walkers to be cautious after his puppy was "mauled" on Hampstead Heath.

James Brilliant was walking five-month-old Rupert near Parliament Hill on Sunday (September 12) when he said the cavapoo was attacked by an ex-racing greyhound.

Rupert was badly injured and forced to have emergency surgery, with vet bills totalling £1,200.

Ham & High: The puppy was badly injured in the attackThe puppy was badly injured in the attack (Image: James Brilliant)

James told the Ham&High: "Rupert was just padding along and exploring a family standing around.

"Their greyhound didn't like it, and suddenly grabbed him in his mouth, picked him up off the floor and viciously mauled him.

"Rupert was hysterical and crying out in agony."

People watching the scene unfold were screaming and panicking, he said, and James said when he attempted to prise the greyhound's jaws open it bit his hand.

Others tried pouring water over greyhound and pulling on his lead to force it to drop the puppy, and after around 30 seconds its grip loosed.

"We were all so shocked, and there was a lot of blood- Rupert was clearly badly injured," James added.

"But he's really fluffy, so it was difficult to see the full extent of the damage."

Ham & High: Rupert has had a drain fitted to remove fluid build-up around the woundRupert has had a drain fitted to remove fluid build-up around the wound (Image: James Brilliant)

Ham & High: The puppy's vet bills came to more than £1,000The puppy's vet bills came to more than £1,000 (Image: James Brilliant)

James exchanged contact details with the greyhound's owners, who he said were also shocked by what had happened.

At a Hendon vet, the shaken puppy was sedated as medics operated on his injuries.

James explained "The vet said that he was lucky to be alive, as the bite could have easily pierced an organ.

"To hear a puppy screaming is just the most horrific sound."

Now Rupert is recovering at home, but the Belsize Park man fears other dogs could face a similar fate.

"Two whippets mauled my neighbour's cat a few months ago," James claimed.

"And another puppy in the group I attend had a similar experience to Rupert.

"Racing dogs are hard-wired to catch fluffy animals, and the Heath and Primrose Hill are very busy with dogs.

"Owners should be aware of this risks, because as, in seconds, everything can change.

"I'm not blaming the dogs, or even their owners, but people need to be aware of what can happen."

Ham & High: James was walking Rupert in Parliament Hill when the attack took placeJames was walking Rupert in Parliament Hill when the attack took place (Image: James Brilliant)

Since the attack, James said Rupert has been a "different dog" and his personality has drastically changed.

"I just hope there is no long-term trauma," he added.