The question of empire has become central to discussions of Britain’s national past. Some see residual imperialism as the prime element in a deficient, delusional, racist culture. Others think emphasising the dark underside of empire is an attempt to erase British history. The problem is that although long historical tradition sanctions criticism of imperialism, national history has proved far more resistant.

Talk of empire is now omnipresent, but it was previously written out of history. In the 1940s the unashamed imperialist Winston Churchill didn’t offer an imperial history of the second world war, or even a national one, but an Anglo-American, cold-war version of events in his six-volume work, The Second World War. Subsequently, what’s striking about postwar historiography is the lack of imperialist histories and the absence of condemnation for nationalist and anti-imperial forces. At most there were sotto voce claims that the British empire should have done a deal with Adolf Hitler in 1940 to keep itself alive.

More importantly, national histories ignored empire altogether. The reason is easy to find: after the war, a new nation arose that wanted to tell a national, not imperial, history of itself. This story was about the dawn of the welfare state, the Labour party and the National Health Service. This country’s ancestry lay in the industrial 19th century, but it only became a true nation in 1940, during the Battle of Britain and the blitz.

Putting the empire in its proper historical place is hugely important for understanding the sheer scale of slavery, the racialised nature of the imperial project, and how this project shaped the Conservative party into the 1950s. For much of the elite, the UK was seen as a part of something far bigger: the empire. This is why we have an Imperial War Museum and an Imperial College, and why the head of the army was called the chief of the imperial general staff. Britain’s second world war, as it was understood at the time, involved the whole British empire (and many, many allies). In 1940, no one in authority could say “Britain stood alone”. If anything was alone, it was the entire empire.