The second art that I acquired in Pentonville was so-called ‘Marseilles chess’. It was invented by an elderly Frenchman, with a red scarf round hs neck, who taught it to me during exercise hours. In this game, each player in turn makes two moves instead of one – the only restriction being that the first of the two moves should not be a check to the King. To the chess-addict this is a nerve-racking experience which shatters his outlook and upsets all his values. Hitler and the Gestapo have faded into the past, but the memory of Marseilles chess in Pentonville still makes me shudder.

Arthur Koestler, Scum of the Earth (1955)