As a harbinger of a gradual shift in global power it is easy to miss: a discreet red, blue and green banded symbol bearing the mysterious legend UnionPay. But walk into Harrods, Selfridges and other high-end stores and you will see it at many tills, meaning the shop accepts China's most popular bank card and is thus actively chasing income from one of the few global economies still expanding at speed.

China accounted for just under 110,000 visits to Britain last year, a 23 percent annual increase. Of equal significance for retailers, the overall spend by Chinese nationals rose even faster, by 57 percent. The trend appears to be accelerating, with VisitBritain recording a near-doubling of the spend per Chinese tourist during 2011.

A spokesman for Selfridges said sales to Chinese customers had in recent years "consistently achieved high double-digit growth numbers".