When, 50 years ago, I read out of curiosity the entry for Edinburgh in an ancient edition of the Larousse dictionary, I was astonished – “capitale de l’Écosse, située sur la Leith.†Nowadays, more realistically, it is “sur l’estuaire du Forth.†Yet at one time the role played by Edinburgh’s River, the Water of Leith, in the economy of the town and its surroundings was vital.