When turbaned warriors from Daesh (or Isis) advanced on Raqqa in Syria two years ago, they whooped wildly about having ‘broken the Sykes-Picot Agreement’. They were celebrating athe destruction of national frontiers which had stood for nearly a century, since the fall of the Ottoman empire in 1918.

They were also venting their spleen against the two villains (as they saw it) of the piece — one British, Sir Mark Sykes, and the other French, François Georges-Picot, who, after months of diplomatic haggling, had drawn metaphorical lines in the desert sand to reach their secret 1916 agreement apportioning Ottoman lands and...