Codebreaker Max Newman worked at the Government Code and Cypher School (GC&CS) at Bletchley Park. His problem was how to get a machine that would help turn German coded radio teleprinter messages into ordinary language. A group of Post Office telephone engineers led by Tommy Flowers worked out how to do this. Their design, which was called "Colossus" used many vacuum tubes (valves). The first machine, Mark 1, worked in December 1943 and solved its first problem in February 1944. Colossus Mark 2 was even better. It first worked on 1 June 1944, just before the Normandy Landings on D-Day. Ten Colossus computers were in use at the end of the war.