In the taxi, Smith began to speak. 

"I must tell you something, Petrie. The world today has an enemy. He is a great scientist. He is one of the greatest thinkers in the world. But perhaps there is no man worse than him on earth. He is very dangerous." 

"Who is this man?"

"Dr Fu Manchu."

This gives the flavour of the popular Edwardian pulp-fiction writer Sax Rohmer. His most famous work was The Mystery of Dr Fu Manchu. It is marvellous stuff, with toxic green gas and a killer red ant, all the action oscillating between fog-bound Limehouse and Fu Manchu's victims in Belgravia's stucco terraces, where he drugs and kidnaps leading scientists.

Rohmer was indebted to an earlier writer called Matthew Shiel, whose serialised story  The Empress of the Earth (1898) featured the Chinese criminal mastermind Dr Yen How. Both writers played on fears which can be traced back to Kaiser Wilhelm's mania about die Gelbe Gefahr, for the mad Emperor saw himself as the Archangel Michael leading Europe's nations against the "yellow peril".

Amidst all the entirely justified concerns about what Jack Straw called "Pakistani-heritage" Britons, together with Bangladeshis the main drivers of Islamist extremism, we tend to lose sight of other significant minorities who make a valuable contribution to life in this country. They include around 400,000 British Chinese, a minority which both integrates and actively eschews any attention this column may give it.

Chinese sailors were recruited into the merchant navy during the Napoleonic Wars, to release native tars for the Royal Navy. During the 19th century, some settled around the docks in Limehouse and Poplar, as well as Cardiff and Liverpool. Lurid reports of opium dens and white slavery attracted the more venturesome high-society bucks, although the reality was of small "chop houses", so-called because of their individual signs, and steam laundries.