By Graham Satchell
Pit bull terriers are a popular breed for young men to own
In a desolate back street in Middlesbrough, a group of young men are shouting and holding back two pit bull-type dogs.
It is out-of-focus, grainy footage shot on a mobile phone and hard to watch.
In total there are two-and-a-half minutes of dogs fighting, clamped to each other. It is the sound that is most stomach-churning.
The footage was acquired by the RSPCA and used to convict and sentence two men to five months in prison.
The RSPCA is now holding a conference to tackle what it calls "one of the UK's most pressing social issues".
They are talking about dogs being used as status symbols to intimidate and to fight.
In London I joined RSPCA inspector Sam Garvey on patrol. She is despondent about a trend she sees every day - young men with vicious-looking dogs hanging out on street corners.
"There are people that are using dogs," she says, "because they know that they can't have a gun, they can't have a knife.
"So instead they'll have 42 teeth on the end of a lead. That's keeping other people away from them."
New figures from the RSPCA show a dramatic rise in the number of dog fights reported to them by the public - up from 24 in 2004 to 358 last year.
The charity says it is the owner causing the problem, not the dog. All types of dog can be trained to be aggressive, they claim, just as all types of dog can be loving family pets.
So what to do about so called "dangerous dogs"?
Four types of dog are banned under the 1991 Dangerous Dogs Act. But the legislation is widely discredited.
There have been endless legal squabbles in court about the exact definition of the word "type".
The RSPCA says the legislation is flawed, the focus is wrong. They want emphasis shifted from the dog to the owner or, in their catchier phrase, "the deed not the breed".
They will suggest at their conference that all owners get their dogs micro chipped, that more effort is made to educate owners before they buy dogs and that more dogs are neutered.
'Traumatic and terrible'
So what does the government make of this?
The Department of Environment, Food and Rural Affairs (Defra) is to release a new leaflet.
They say it will provide clear, concise and accessible information about the law on dogs which are dangerously out of control and dogs which are banned.
The government also says it has reviewed all existing laws and that they are tough enough to call irresponsible owners to account.
Meanwhile, in a park near Putney in south London, I meet Mike Ebberson. On 21 October last year, also his birthday, he was walking his dog Millie just a couple of hundred yards from his home.
Two pit bull type dogs swooped on Millie. Mike tried to fight them off but they turned on him.
"They came out of nowhere," he says.
"One dog actually bit straight through into my arm. That was down to the bone. I've had to have 25 stitches in there."
After nearly half an hour an armed unit of the Metropolitan Police arrived. They managed to wrestle one dog away. The other was shot four times before it loosened its grip. Mike's dog Millie died.
"I've never seen such a rabid dog before. I've never felt power like that before. It was just so traumatic, the whole incident was just terrible."