The British establishment promotes a strange myth about the British Empire.

Though it was the biggest empire the world has ever known, built on slavery and gunboats, our rulers argue that it was somehow a gentler, nicer colonialism.

The release of an archive of “lost” colonial documents last week undercuts this nonsense.

They show that in the early 1940s the British government seriously considered testing chemical weapons in Bechuanaland, now Botswana.

In the 1950s it practised brutal collective punishment on any Kenyans who were suspected of supporting the Mau Mau independence movement.

And it “eliminated” the colonial authority’s enemies in Malaya....