History teaches us that empire can bring out the worst in people. In Britain we applaud the "civilising mission" of our imperial past, but are less happy to acknowledge the violence and brutality that so often girded our imperial endeavour. It is time we were more honest.

As a nation Brits nurture memories of empire that are deceptively cosy, swathed in a warm, sepia-tinted glow of paternalistic benevolence. The British empire, so the story goes, brought progress to a primitive and savage world. Education, hospitals and improved health, steamships, railways, and the telegraph – these were the tools of empire, brought to colonised peoples by the gift of commerce and good British government.

We take pride in this imperial heritage, pointing with scorn at the lesser achievements of other European powers – the French, Italians, Germans, Belgians and Portuguese – whose empires we variously view as haplessly mismanaged, malignly exploitative and brutally coercive. Britain's empire was better than all the others, historians such as Niall Ferguson, Andrew Roberts and Lawrence James have assured us, so why should we worry?

The reasons to worry became all too apparent last week, in a path-breaking judgment of the high court: Mr Justice McCombe ruled that the British government has a case to answer in relation to charges of systematic torture and abuse of detainees during Kenya's Mau Mau rebellion of the 1950s.

And the matters raised are far from trivial...