Dr Tom Flett, born 100 years ago from an Orkney family in Glasgow, took his PhD at Cambridge under the supervision of one of the greatest mathematicians of the time, John Littlewood and went on to become professor of mathematics at Sheffield. But he is better known across Scotland and further afield as the co-author with his wife Joan of the classic book Traditional Dancing in Scotland, which gathered together a wealth of information about dances and dancers. Their daughters Jane Harrison and Lindsay Smith tell the family story, and a mathematician looks at the mathematical background.