Appendix: Timeline of Key Events

September 1939	Bletchley Park is set up to provide a hub for intelligence and codebreaking work for the war effort.
1940	The first complement of WRNS members arrive at Bletchley.
March 1940	The first of the electromechanical Bombes is installed at Bletchley.
July–October 1940	The Battle of Britain, the most intense period of German aerial bombing of major British cities during the Blitz, contributes to more lives being lost on the home front than at the actual front.
December 1941	Britain begins conscripting women workers for the war effort. Initially all women between the ages of twenty and thirty-one are called up for service in wartime industries, except for mothers of children under age fourteen.
Summer 1941	WRNS operate over 200 electromechanical Bombes to help speed codebreaking.
June 1943	The faster but unreliable Heath Robinson machine starts to be used for codebreaking the more complex Lorenz cypher.
December 1943	Colossus becomes operational at Post Office Research Station owing to the efforts of Tommy Flowers and his team.
January 1944	Colossus is shipped to Bletchley Park. It is operated and programmed by the WRNS, using William Tutte’s “statistical method” for codebreaking.
Early 1944	Joan Clarke becomes deputy head of Hut 8, the area of Bletchley involved in hand-codebreaking.
June 1, 1944	Colossus II is assembled and tested at Bletchley and becomes operational, providing crucial intelligence information for the success of the D-Day landings.
September 1945	Members of the WRNS destroy all but two Colossus computers on Churchill’s orders. The remaining two are moved to GCHQ for intelligence and research. The last of the two remains operational until 1960.
1946	The marriage bar is repealed in government, technically allowing women to keep their jobs after marriage. In practice, however, it changes little.
1948	The Machine Grades are created in the Civil Service.
May 1949	The EDSAC, which formed the basis for the LEO I of 1951, becomes operational at the University of Cambridge.
Summer 1949	The Manchester Mark I runs the first stored program. It is commercialized as the Ferranti Mark I, the first of which is delivered in February 1951.
1950	The National Physical Laboratory Pilot ACE becomes operational. Led by Alan Turing, this project would become the basis for English Electric’s commercial line of DEUCE computers.
1952	The Great Smog kills several thousand Londoners owing to the fact that only low-quality, dirty-burning coal is available off ration to citizens for home heating.
1954	Wartime rationing ends.
1955	Equal Pay for government employees is introduced. Unequal pay remains legal in private industry.
1957	The Windscale nuclear weapons plant catches on fire, leading to Britain’s worst nuclear disaster.
1959	Powers-Samas and British Tabulating Machines merge to form ICT.
1963	Wilson declares a “white hot technological revolution” is necessary to save Britain’s global standing. Wilson is elected prime minister the following year.
1963	Ferranti merges with ICT.
1963	Britain attempts to join the EEC and is rejected.
1963	English Electric and LEO Computers merge to form English Electric–LEO.
1964	The Ministry of Technology is created by Prime Minister Harold Wilson.
1967	Britain attempts to join the EEC and is rejected for the second time.
1968	International Computers LTD (ICL) is created through a government-backed merger of English Electric LTD and ICT LTD; the government promises the company preferential treatment in government contracts in return for influence over their product line.
1971	The Heath government begins to distance itself from ICL, removing price protections and allowing departments the option of buying IBM computers.
1973	Britain joins the EEC.
1974	A series of strikes in industry and government, including strikes by computer workers, prompt Prime Minister Edward Heath to implement the “three-day week” and declare more states of emergency than any previous prime minister.
1975	The existence of the Colossus computers is revealed to the public, despite government reluctance, after decades of being kept secret under the Official Secrets Act.
1975	A National Equal Pay Act, passed in 1970, comes into force, and a National Sex Discrimination Act is passed as a requirement of Britain’s entry into the EEC. The measures do little to equalize women’s position and the EEC brings infringement proceedings against the United Kingdom in 1975 as a result.
1978–1979	Labor union strikes during the “Winter of Discontent” wrack government and industry.
1983	The EEC censures Britain for not enacting the gender equality standards required of EEC member states.
1990	Fujitsu acquires an 80 percent stake in ICL.
1998	ICL becomes a fully owned subsidiary of Fujitsu.
2002	The ICL name is dropped.
2008	A working replica of Colossus II is completed at the National Museum for the History of Computing in Block H of Bletchley Park—the original site of the Colossus computers. In the years following, many women whose stories were nearly lost come forward to talk about their secret wartime computer work.