It was one of those tweets by a public body you couldn’t quite believe. “Here’s today’s surprising #FridayFact,” HM Treasury declared last week. “Millions of you helped end the slave trade through your taxes.” Attached to the tweet was an image of slaves in chains with the caption: “In 1833, the British government used £20m, 40% of its national budget, to buy freedom for all slaves in the empire. The amount of money borrowed for the Slavery Abolition Act was so large that it wasn’t paid off until 2015. Which means that living British citizens helped pay to end the slave trade.”

The slave trade was actually abolished in 1807. The 1833 Slavery Abolition Act abolished, as the name suggests, slavery itself. A Treasury so loose with its facts might explain something about the state of the British economy. Worse, however, was the claim that British taxpayers helped “buy freedom for slaves”. The government certainly shelled out £20m (about £16bn today) in 1833. Not to free slaves but to line the pockets of 46,000 British slave owners as “recompense” for losing their “property”. Having grown rich on the profits of an obscene trade, slave owners grew richer still from its ending. That, scandalously, was what the taxpayer was paying for until 2015.

The Treasury deleted its tweet on Saturday morning. It is, however, part of a long tradition of the British authorities playing down their central role in the transatlantic slave trade, while claiming credit for ending slavery. It was not Britain but slaves themselves and radicals in Europe who began the struggle against enslavement. Nevertheless, the “moral capital” of abolitionism, as historian Katie Donington observes, continues to provide “a means of redeeming Britain’s troubling colonial past”.