In the summer of 1939, as war broke out, a group of scholars who were going to become codebreakers arrived at Bletchley Hall. They pretended to be a shooting party - a group of friends going to stay in the country to do some shooting.

Their mission: to crack the Nazi Enigma cypher. The odds against them were a staggering 150,000,000,000,000,000,000 to 1. Their success in breaking this seemingly 'unbreakable' code was one of the greatest intellectual achievements of the twentieth century.

And in Colossus, they gave us the world's first computer, built to crack the Lorenz cypher used by Hitler and his generals. These WRENS worked on Colossus, which was an early computer.

The work of Bletchley Park's pioneers secretly affected the fate of nations during the course of the war and helped shorten it by at least two years. Since then, millions of people have been influenced by what happened on and beyond this site.

Over 10,000 people worked here at the height of the Park's wartime activity. Working conditions were cramped and spartan, and they often worked in tiny huts in the grounds. The work itself often very hard. But for many recruits, it was the time of their lives. Here they are playing rounders during a break in their work.

By March 1946 they were all gone, removing every scrap of evidence of their codebreaking exploits as they left. Their efforts in breaking those 'unbreakable' codes in the utmost secrecy caused Winston Churchill to coin the phrase "the geese that laid the golden eggs and never cackled". It would be decades before Bletchley Park would start to reveal its secrets. None of the people who worked there were allowed to tell anyone what they were doing - not even their own families.