Allied sailors visiting an Algerian port towards the end of the Second World War probably felt a little puzzled. Not by the barnacled warships cluttering the harbour of Mers-el-Kebir, but by the fact that they were French and had been sunk by the British. The story of why Churchill ordered the navy to attack his ally has been described as a tragic collision of Gallic pride and clumsy British diplomacy.
For the man in charge it was "the greatest political blunder of modern times". That man, Admiral Sir James Somerville, was the commander of Force H, a fighting fleet that on July 3, 1940, was off Mers-el-Kebir. Only days before, Hitler had forced France to its knees. Now Churchill was worried that the fleet that flew the Tricolor, the fourth largest in the world, might fall into Nazi hands. Churchill gave the French navy four options: join up with us, sail to a British port, sail to an American port, or scuttle your ships where they are. Refusal would reap destruction.
Somerville was not impressed by the scheme, fearing it risked converting a defeated ally into an enemy. He told Churchill so - which didn't do his subsequent career much good.
At anchor in Mers-el-Kebir was a large chunk of the French navy under Admiral Marcel Gensoul. Unfortunately he was miffed because the British had sent a mere captain to negotiate terms. Poor Cedric Holland, a lover of France, realised the talks were going badly. Gensoul's orders were not to let his ships fall into the hands of any foreign power. And he resented negotiating at the point of a battleship's gun.
Time was running out. At 5.26pm Somerville was forced to give Gensoul a 15-minute warning. Before Holland even got back to the safety of his own vessel the British had opened fire. Three French battleships and 1,300 sailors were lost because their governments could not come to terms.
Somerville knew he would be criticised for letting one warship escape. But he told his wife: "It was an absolutely bloody business. The truth is my heart wasn't in it."