The brilliant work carried out by British codebreakers based at Bletchley Park is now believed to have shortened the duration of World War II by up to two years. But during the dark days of 1941, as Britain stood almost alone against the apparently unstoppable tide of the Nazi war machine, this remarkable achievement seemed a million miles away. With the help of their Polish counterparts, the British codebreakers had broken the German Enigma machine cipher. But the resources on which they could call were so small that it seemed their achievements would be in vain. Without the necessary manpower, they would never be able to take full advantage of their ability to break the German codes and ciphers. In October 1941, four of the leading codebreakers, including the outstanding Alan Turing, wrote a letter to Winston Churchill asking for help. Reminding him that on a recent visit to Bletchley Park he had praised their work, they told him that it was being held up and in some cases not being done at all, principally because we cannot get sufficient staff to deal with it.