The Yesterday channel’s ongoing “Spirit of 1940” season has provoked a giant surge in its viewing figures, another reminder of the grip World War Two still exerts on large chunks of the British public. The Battle of Britain in particular has become a self-contained historical moment emblematic of what the British regard, or at least used to regard, as their finest characteristics – patience, courage, stoicism and a dogged refusal to accept bullying European dictatorships. Maybe we haven’t quite let go of that last part. Perhaps the story of our Boys in Blue in the late summer of 1940 gains additional resonance from the way it contrasts so starkly with the meandering aimlessness of Britain’s recent military adventures. It was a battle with a purpose, won by the Brits without any help from the Americans.