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British Industrial History

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Thomas Harold Flowers

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Thomas Harold Flowers (1905–1998), engineer

1905 born on 22 December at 160 Abbott Road, Poplar, the son of John Thomas Flowers, bricklayer, and his wife, Mabel Emily, formerly Richardson.

Flowers gained a scholarship to attend technical college.

1921 Served a four-year mechanical apprenticeship at the Royal Arsenal in Woolwich, and at the same time attended evening classes, gaining a London University degree in engineering.

1926 Flowers joined the Post Office as a probationary inspector in the engineering department[1]

1930 He moved to the Dollis Hill laboratory as probationary assistant engineer[2] (electrical engineer)

1935 Married Eileen Margaret Green. The couple had two sons, Kenneth and John.

Flowers built up considerable expertise in the use of valves, in particular developing systems of valve amplifiers and switches that by 1939 enabled long-distance calls to be made without the intervention of an operator.

1938 He was security cleared for work on radar.

1939 August: he travelled to Berlin for a technical meeting, returning just in time, on the last boat train, before the outbreak of war. At this time, Flowers was possibly the only person in Britain who realized that valves could be used reliably on a large scale for high-speed digital computing

WWII Assisted C. E. Wynn-Williams, at the Telecommunications Research Establishment, who designed high-speed machines for the comparison of enciphered free text messages.

1943 Executive Engineer, General Post Office. Awarded OBE[3]

Largely as a self-supported sideline at Dollis Hill, Flowers and his team began in February 1943 to design and construct a prototype machine that could store information electronically whilst avoiding the presumed problem of the unreliability of electronic valves. As a result the Colossus, containing 1500 thyratron valves, was demonstrated on 8 December 1943, running for eight hours without fault.

Early 1944: Nazi communications security was tightened; high-speed code-breaking techniques, such as had been demonstrated with Colossus, became essential. Needing greater production capacity, Flowers proposed to take over a Post Office factory in Birmingham. Final assembly and testing of the computers would be done at Dollis Hill. Colossus mark II, a full-scale version of the prototype, using 2500 valves, was completed by Flowers's team 5 days before D-Day.

Ten Colossus machines were in operation by the end of the war.

Flowers later received £1000 compensation — less than he had spent.

Post-War: Flowers returned to telephony at Dollis Hill, where he was head of the section developing electronic switching, forerunner of the subscriber trunk dialling (STD) system introduced in the following decades.

He also assisted the National Physical Laboratory's project to build the ACE computer.

As Post Office chief engineer Flowers designed an electronic random-number generator, ERNIE, operational from 1957, to pick winners among holders of premium bonds. This was a public success.

1964 Having fallen out with Post Office management about the design of future exchanges (they had decided to use pulse code modulation), Flowers moved to STC to continue work on analogue switching.

1970 Retired from STC

1998 Flowers died at his home in Mill Hill, London, on 28 October.

See Also


Sources of Information

  1. London Gazette 1926
  2. London Gazette 1930
  3. London Gazetter 4 June 1943
  • Wikipedia
  • Biography of Thomas Harold Flowers, ODNB
  • The Sacking of Tommy Flowers by Jork Andrews [1]