Helpers of the hounded: Mark Handscomb on a roving, alternative clinic that treats homeless people's pets

Standing 6ft 5in in his bare feet, and naked except for a pair of skimpy shorts and white goatee beard, Henry is off to the vet. In his hand, he proudly clasps his dog's vaccination certificate as though it were his only piece of property. Henry's scabby-looking mongrel, Max, snarls at all the other dogs. 'I called him Max because he looks like the dog out of the film Mad Max,' says Henry. 'He's got that look on his face.'

Henry is no ordinary customer and this is no ordinary vet: Homeless Owners With Pets (Hope) is a voluntary outreach organisation which delivers a free service to pet owners who have no fixed address.

'If you've no home and you've lost your ties with your family, your dog is often your only lifeline,' says Colette Kase, a dog trainer and pet counsellor who was herself once homeless and now co-ordinates Hope in her spare time. 'Since these owners are never going to be able to afford conventional veterinary care, we hope the vaccination service we offer will keep their pets healthy and happy.'

I met Colette on one of Hope's regular Sunday afternoon clinics in London. Previous clinics have been held underneath railway arches; this week it was Claremont Road, a street in suburban Leyton where opponents of the M11 motorway extension have been squatting.

The vet for the day is April Jones, who has her own private practice in London. Today, she has spurned the traditional white coat for leggings and a baggy T-shirt. Sporting cropped hair, she is Britain's only black woman vet.

The third member of our troop, 25- year-old Rachel Pelon, looks more like a hippy squatter than a veterinary nurse. Wearing biker boots, chains and chrome-framed sunglasses, only the tattoo of a startled cat on her bosom suggests she might be more interested in the pets than protesting against the motorway.

Armed with a bottle of water to keep the effects of the blistering heat at bay, we arrive with a rucksack full of flea collars, syringes and vaccine.

Enter Claremont Road from the main road and you walk into another dimension. The conventional brick terrace houses prickle with scaffolding to deter bailiffs. Some have been brightly painted, others daubed with slogans.

Four tree-houses occupy the upper branches of the plane trees opposite. Huge nets have been suspended above the road, providing summertime hammocks for those brave enough to sleep over the tarmac. Grass grows out of the engine and interior of a battered estate car.

Through a heavy corrugated iron gate lies the inner sanctum of the Claremont Road squatters. We are greeted by Offshore, a circus entertainer who is still wearing his pyjamas. Through a mouth full of gold teeth, Offshore loudly announces he does not believe in veterinary care - it 'weakens the species' - and bellows at his two alsatians, Khrushchev and Stalin, to avoid us. Obediently, the dogs retreat underneath their master's double-decker bus and observe from a distance.

Inside the rubble-strewn encampment, the protesters and travellers watch as a large table is cleared of rubbish and a makeshift surgery is established beside the squatters' garden. Carefully tended geraniums and cannabis plants nestle beside two battered armchairs. Two loudspeakers, pulsating with New Age music, have been positioned beside a judas tree. Semi-clothed youths wander about, practising their pan pipes.

'At least 25 per cent of people in conventional homes have pets, so it's reasonable to assume that the same proportion of people on the streets are pet owners,' says April. 'I'm concerned not just for the welfare of the pet but for the owner, too, because the dogs are their closest link to the world.

'At the private practice I normally work in, we get a lot of dogs who are overweight or over-pampered. The dogs out here are a lot healthier. They are also better behaved.'

But not all of them. Henry's dog, Max, has the pitiless, black-eyed stare of a shark and swaggers like a pit bull terrier. His brown coat is scarred from fighting, although his silver-haired muzzle betrays his advanced age. I decline to pat him on the head and murmur encouragement.

As packs of dogs swirl around our legs, sniffing each other and cocking their legs, I wonder about the hygiene implications of having 20 dogs roaming the street. 'Sometimes it gets a bit much,' says Henry, 'and we have a 'pooh' patrol to clear it up a bit. But we have got patches of grass where they go.'

A casual procession of dogs and their owners drifts back and forth. Bald patches and mange are pointed out, pets are prodded and stroked. Flea collars and worming pills are handed over. Eager hands rummage through a brightly coloured pile of leads and chains, while Colette makes sure they are fitted properly.

'They have all come from members of the public,' she says. 'A lady in Northern Ireland, whose dog had died, sent me a collar and lead, hoping someone else might be able to use it.

'From a dog perspective, their quality of life is very high. Unlike many pets who are abandoned during the day while their owners go out to work, these dogs can come and go as they please and have no shortage of playmates.'

It's not all fun for a homeless dog, though. 'We've had two or three sets of bully boys come down here with baseball bats just standing at the end of the road intimidating us,' says Henry. 'Having the dogs around makes people in the street feel safer.'

Hope features in '3D' on ITV tonight at 7.30pm.

(Photograph omitted)