The series was influenced by the internationally successful Charlie Chan detective films of the 1930s and '40s, but in line with industry attitudes of the time, that particular Chinese detective was invariably played by a white actor in 'yellow-face'. The BBC's update of the archetype, cast the British-born Chinese actor David Yip as Detective Sergeant John Ho. Instead of the barely intelligable English typically spoken by Chinese actors in British drama, Yip's accent has a strong Cockney influence. Ho fits the pattern of the maverick detective, prepared to use unorthodox methods to solve his cases, which emerged in series like Z Cars (BBC, 1962-78) and further developed in The Sweeney.

The series was influenced by the internationally successful Charlie Chan detective films of the 1930s and '40s