This is untrue,

Cotton was the leading American export from 1803 to 1937.”What did cotton production and slavery have to do with Great Britain? The figures are astonishing. As Dattel explains: “Britain, the most powerful nation in the world, relied on slave-produced American cotton for over 80 per cent of its essential industrial raw material. English textile mills accounted for 40 percent of Britain’s exports. One-fifth of Britain’s twenty-two million people were directly or indirectly involved with cotton textiles.”