Interview with Thomas Harold Flowers

British schoolchild Bromley-by-Bow, London, GB, 1914-1918; electrical engineer with General Post Office in London, 1926-1930; research engineer with Post Office Research Station, Dollis Hill, GB, 1930-1941; research engineer developing Colossus computer at Post Office Research Station, Dollis Hill and Government Code and Cypher School, Bletchley Park, GB, 1941-1945

REEL 1 Background in Bromley-by-Bow, London, GB, 1905-1926: family; education and interest in mathematics; sporting activities; eye accident; interests in modelling and motors; attending East Ham Technical College; memories of First World War, 1914-1918, including German Zeppelin attacks and aircraft raids, rationing and Armistice celebrations, 11/11/1918; nature of scientific education at East Ham Technical College. Aspects of period as electrical engineer with General Post Office in London, 1926-1930: passing entrance examination; duties testing telephone equipment at Post Office Stores Depot, Islington, 1926; role as electrical engineer with Circuit Laboratory at King Edward Street Post Office. REEL 2 Continues: attending evening classes in telephone engineering; lack of formal training with General Post Office; practical as opposed to theoretical knowledge of former British Army signallers. Recollections of period as research engineer with Post Office Research Station, Dollis Hill, GB, 1930-1941: design, manufacture and testing of automatic exchange equipment; explanation of relay and ratchet electrical/mechanical switches; method of problem solving; automatic dialling system operating electrical switches; problems in equipment connecting automatically to correct exchanges; method of connecting automatic and manual exchanges; necessity of working at home; absence of concept of computer; overcoming problems and successful introduction of automatic exchanges; role studying problem of long distance dialling and background to introduction of electronic valves to replace mechanical switches. REEL 3 Continues: successful long distance dialling tone trials between London and Bristol and subsequent value of system during German Air Force raids, 1939-1945; question of international co-operation on telecommunications and work of commission established under League of Nations; method of distinguishing between dialling tones and speech; pay and question of moving to private industry; question of awareness of approach of war and Reserved Occupation status; opinion of research heads Bertram Cohen and Gordon Radley; organisation and composition of research groups; hours worked; working from home; reaction to declaration of Second World War, 3/9/1939. REEL 4 Continues: emergency evacuation to GB during visit to meet telecommunications scientists in Germany, 9/1939; work on developing radar stations communications system for Royal Air Force, 1939-1941. Recollections of period as research engineer developing Colossus computer at Post Office Research Station, Dollis Hill and Government Code and Cypher School, Bletchley Park, GB, 1941-1945: meeting with Alan Turing and his explanation of technology of code breaking in connection with German Enigma coding machine, 2/1941; background to failure of initial machine to decode Enigma; opinion of Alan Turing; German introduction of teleprinter 'Fish' code; decoding significance of receiving copy of 'Fish' message duplicated in clear transmissions; Max Newman's role in devising mathematical process to determine setting of code wheels; taking over project after failure of team originally assigned to develop code breaking 'Robinson' mechanical machine based on teleprinter due to problems in driving paper tape sprockets; decision to abandon 'Robinson'; developing concept of using electronic valves switching to get necessary processing speed. REEL 5 Continues: principles of German Lorenz SZ42 coding machine producing 'Fish' code; developing concept of electronic Colossus machine to reverse coding procedure; testing possible speed of imput paper tape; decision not to commission Colossus from Post Office Research Station as result of questions of reliability of electronic valves and completion time required; decision to manufacture Colossus on own authority and formation of special team at Post Office Research Station assisted by Post Office telephone equipment factory; method of designing and 'programming' of Colossus to determine Lorenz wheel positions; manufacture of prototype Colossus, 2/1943-12/1943; refinements to Colossus design to introduce quicker parallel processing and preparations to manufacture further machines despite initial lack of reaction from Government Code and Cypher School at Bletchley Park; emergency orders from War Cabinet to prepare 12 Colossus machines by 1/6/1944; intense work rate; successful production of Colossus and eradication of initial fault by 1/6/1944; second hand reports of role of Colossus machine in decoding German messages which assisted General Dwight D Eisenhower in making his strategic decision over Operation Overlord; assignment to produce electronic machine to use results of automatic radar tracking to lay anti-aircraft guns, 1944-1945; question of concept of Colossus as computer with memory, programme and processor; question of Alan Turing's minimal role in development of Colossus. REEL 6 Continues: difficulty in explaining concept of Colossus to decoding staff at Government Code and Cipher School, Bletchley Park; question of Alan Turing's minimal role in development of Colossus; work of Professor Brian Randell in defining of Colossus as first computer, 1975; story of German scientist stopped from working in same field, 1939-1945; Colossus attachment developed by mathematicians to break German code changes; award of honorary doctorate; state of health of Colossus team; work on memory devices for electronic machines and question of duplicated research. Post-war career with Post Office Research Station at Dollis Hill, GB, 1945-1965: ban on working on computers and destruction of Colossus machines; work on valve telephone exchange; superiority of transistors; question of effect of secrecy and delays in research work; being given Charles Babbage Award, 1998.