Rome fell. Babylon fell. Hindhead’s turn will come.” George Bernard Shaw’s bon mot in Misalliance was a reminder to British theatre audiences in 1910 that all empires eventually decline and fall. The fact that Hindhead is an English village was a light-hearted cloak for a serious point.

As an Irishman, Shaw may have found it easier than the English to joke about the decline of the British empire. But, these days, it often falls to British academics based in America to play the role of the insider-outsider, commenting on the decline of today’s pre-eminent global power, the US. In the long-running debate about the future of American power, some of the most influential “declinists” are British historians working at American universities: Paul Kennedy at Yale, Niall Ferguson at Harvard and Ian Morris at Stanford.

This British tendency to believe that America’s “empire” will decline is more than just a curiosity of intellectual debate. It also has real-world effects. Behind the scenes, many British policy makers also seem to be operating on the assumption that the continuing rise of China and the relative decline of America are both inevitable. As a result, they are making decisions that reflect a cautious adaptation to this wind of change. Britain’s recent decision to defy Washington and join the China-led Asian Infrastructure Investment Bank is one straw in that wind.