It was Sept 4, 1939, the day after the UK declared war on Germany, when mathematician Alan Turing reported to work at the Government Code and Cypher School
at Bletchley Park
. Within weeks of his arrival, Turing and his colleagues were able to intercept high-level encrypted enemy communication signals and decode a vast number of these messages. The intelligence gleaned from this effort was passed on to field commanders, a process that was decisive to Allied victory.