Gordon Bamford Preston (28 April 1925 – 14 April 2015) was an English mathematician best known for his work on semigroups. He received his D.Phil. in mathematics in 1954 from Magdalen College, Oxford.He was born in Workington and brought up in Carlisle. During World War II, he left his undergraduate studies at Oxford University for Bletchley Park, to help crack German codes with a small group of mathematicians which included Alan Turing.