Mr Hale's death, which happened two weeks ago, is believed to be the latest murder carried out by a group of professional criminals prepared to kill for cash.
David Veness, Scotland Yard's Assistant Commissioner in charge of specialist operations, has revealed to The Independent that the police believe that up to 20 hitmen - possibly more - are operating from the south-east of England.
The Metropolitan Police's Organised Crime Group are investigating the contract killers who hire out their services from pounds 1,000 to pounds 20,000 per murder.
Part of the reason for the upsurge is the greater availability of handguns. Increased rivalry between traditional crime gangs, particularly over drug deals, has also led to a rash of killings.
A north London crime family, which has a reputation for extreme violence, has also been linked to the spate of murders.
But one of the greatest problems the police face in convicting the professional hitmen, and in a small number of cases women, is the secrecy and unpredictability surrounding the criminals involved.
Contract killers are usually hired because they have no direct links with their chosen victim and are therefore unlikely to be traced back to their employer.
An underground network of contacts exists in which contract killers become known to a small group of people. In addition professional killers are feared by other criminals and potential police informers.
The stereotypical image of deals discussed in the back rooms of dingy pubs still holds true for some jobs, but discussions are more likely to take place in greater secrecy and in more salubrious surroundings.
Interviews with hitmen are rare. However in Tony Thompson's book Gangland Britain, a man named "Max", who claims he is a contract killer, said he charged about pounds 10,000 for each job. "It's quite a lot, but people will do it for a lot less than that nowadays. I mean, you can go down the road and get some coke-head teenager to do it for five hundred quid, but will he do it properly?" When asked about what weapons he used, he replied: "You get a nice thirty-eight revolver, snub-nosed, it's very small, very compact, very powerful. It'll rip through people. You get some nice nickel- and lead-tipped bullets ... they leave nice clean holes."
An example of a traditional hit was the pounds 20,000 contract killing of Donald Urquhart who was shot dead in a London high street.
Mr Urquhart, 55, a millionaire businessman, had been walking with his girlfriend in January 1993 when Graeme West ran up to him and fired three shots from a pistol into his head before escaping on a motorcycle.
West was jailed for life. It later emerged that he had climbed the ladder of south London's underworld from club bouncer, debt collecting and eventual promotion to contract killer.
Police suspect that at least three businessmen, who have never been brought to court, were involved in the killing.
Contract killers are sometimes brought in from outside cities to work in areas where they are unknown to the police and criminals. In one of the most extraordinary cases, two men hired a Maori hitwoman from New Zealand for pounds 7,000 to murder a London roofing contractor with whom they had a business feud. Te Rangimaria Ngarimu, 27, was jailed for life in December 1994 for shooting her victim four times in the head and body.
Sex as well as money can be a factor behind hiring a killer. In July last year the wife of a private detective was sentenced to life imprisonment for hiring a hitman to beat her husband to death at their home in Walmley, Sutton Coldfield.
Ethel Trigwell, 43, was said to have taken out a contract on her husband, Barry, 44, with contacts in the Johannesburg underworld.
Mrs Trigwell was having an affair in South Africa and knew her husband was worth more dead to her than alive.
Caught up in a deadly business
Te Rangimaria Ngarimu, Britain's first known woman contract killer, was jailed for life in December 1994 for shooting dead a hospital patient four times in the head and body for pounds 7,000.
Two men hired the Maori hitwoman to murder a London roofing contractor with whom they had a business feud. Te Rangimaria Ngarimu, 27, killed Graeme Woodhatch while he was having treatment in the Royal Free Hospital in north London. The two men who had hired her were given life sentences.
Donald Urquhart was killed by Graeme West for pounds 18,000 in December 1994 as he walked with his girlfriend, Pam Iampithone (with whom he is pictured above), on a west London street.
West, a former builder, was jailed for life after he shot Mr Urquhart three times in the head before fleeing on a motorbike.
He spent four months planning the hit, but was caught after he told a friend, who informed the police. He is believed to have been hired by a business rival of Mr Urquhart.
Brandon Hale, aged 48, who was known to be a heavy gambler, is believed to be one of the latest victims of contract killers.
He was found shot dead in a wood in Highgate, north London, two weeks ago.
He had been beaten as well as being shot above the eye.
Detectives believe that Mr Hale, who had been a prolific gambler and often visited casinos in the West End of London, may have been killed over a row involving betting debts.Reuse content