The wager between Eisenhower and Montgomery is a fitting memento of their turbulent relationship: they disagreed about when the war would come to an end, just as they argued about almost everything else.

It would be hard to imagine two more contrasting characters. The American general: likeable, diplomatic, balanced and gregarious. The British general: egotistical, prickly, brilliant and caustic.

Yet despite their very different personalities, and frequent disagreements, they managed to work together, and won a war together.