The influence of the Triads is hard to judge. There are more than 500 members in Britain and one estimate suggests that 75 per cent of Chinese-run businesses in Soho hand over protection payments - so called "tea money" - to the groups.

Police have identified four main societies operating in Britain: the 14K, Wo Shing Wo, Wo On Lok and San Yee On.

Triad crime is largely confined to extortion, protection rackets, illegal gambling, prostitution and people smuggling.

The National Criminal Intelligence Service and Scotland Yard monitor the activities of the main Triad societies, with the Met operating a specialist Chinatown unit at Charing Cros