We tend to concentrate on transatlantic slavery but there were other varieties. East African slavery as practised by Arabs and stamped out largely by the efforts of teenage Royal Navy midshipmen. Then there was the slavery of Europeans by the Ottoman Turks. An even less well known version was the enslavement of Scottish coal miners and their families in the 17th and 18th centuries. This was slavery as a legal institution, upheld by the Scottish Privy Council who specifically excluded miners from the Habeus Corpus Act of 1701. Whole families, generations even, were condemned to servitude. It was that great historian of the British Mining industry Professor JU Nef (an American) who compared it to the slavery of black people in the US.