Who knows the mind of David Cameron? The British prime minister may see his single-handed fight against the rest of the European Union last week as part of some cunning plan. To spectators, it looked like a pointless and self-inflicted defeat.

One of the keenest spectators will have been the City of London. For the City, the debacle offers a valuable lesson on its long-term stance on the EU: keep your head and avoid getting cornered into fights you cannot win.