Judge Bruce Laughland told George Wai Hen Cheung he would normally have faced 20 years' jail for his crimes but for the 'exceptional mitigating circumstances' - his information into the workings of the Sui Fong triad, one of four Chinese crime gangs operating in Britain.
Cheung's confession and courage in giving evidence against fellow gang members in the face of death threats and social ostracism from the Chinese community meant his sentence was 'far less than the wickedness' his crimes deserved, Judge Laughland told the Old Bailey yesterday.
He said: 'Those who wish to escape the terrifying turmoil of the Triads and in so doing serve the public interest will receive a most generous discount on the sentences otherwise merited.'
The judge said Triad organisations were 'secret, violent and vicious' and preyed on industrious and vulnerable Chinese people.
Cheung, 29, admitted at an earlier hearing a series of offences including grievous bodily harm, assaults, blackmail, arson, theft and supplying cannabis.
Last year he gave evidence against several fellow gang members in a trial at the Old Bailey.
Martin Heslop, for the prosecution, said Cheung was arrested by police after the shooting of a Hong Kong businessman in Chinatown, London in 1991. Cheung approached detectives and agreed to become an informant after being charged with the shooting. In a 1,400-page statement to police he gave one of the most detailed accounts of Sui Fong activities in the UK.
The result, Mr Heslop said, was 'the most significant breakthrough in detecting and combatting the Triads. Never before has an insider been prepared to break the oath of allegiance and provide an insight into . . . the Triads.'