Tommy Flowers

I don't want to downgrade AlanTuring's status as a genius in all possible dimensions - as a CambridgeMathematician, I recognise his great contribution both to pure maths and to the foundations of digital computing. But this is to point to someone else who was in the same building as Turing at BletchleyPark. TommyFlowers' role in the construction of the world's first digital computer has been much less recognised than Turing's until recently but from the little I know was even more significant, once the theoretical foundations had been laid.

This is an interesting opportunity to do a tiny bit of 'real history' using Wiki. Certainly, I believe that Flowers now deserves global credit for his genius and pioneering contribution to our young industry. Again, the RespectedSoftwareExperts issue, both inside and outside the "geek line", is partly one of accurate information - without this, the term "widely respected" is at best skewed, at worst spurious. And I've felt since 1998, when I first heard Flowers in person, that his neglect compared to Turing has also got a lot to do with something FreemanDyson points to: the English speaking world reveres pure scientists far more than the practical inventors that really transform life and provide so much economic dynamism. This problem is much more acute in the UK, much to our commercial detriment.

-- RichardDrake

It's certainly clear that TommyFlowers was the GPO (British Post Office) hardware genius who built Colossus, and as crucial to Bletchley's success as Turing. And certainly more unsung, since he went back to the GPO and his contributions to Bletchley remained classified and unknown until quite recently.

-- Paul Sherlock

It should be remembered that Tommy was also the first person to be awarded the Martlesham Medal by BT. (Martlesham Heath, Suffolk, replaced Dollis Hill as the home of BT research in the 70's)

There were bits of Colossus 'breadboarding' lying around in one of the underground rooms of 'The Paddock' building at Dollis Hill as late as 1960. They were 8 foot 19 inch racks with the unmistakable acorn valves clearly visible.

-- KeithBraithwaite

From AlanTuring:

"Turing was also a thoroughly practical man, and had a lot to do with the design of the hardware used at BletchleyPark and later"

On the other hand, in early 1998 Tommy Flowers said with great feeling to a friend of mine, when Nic referred to AlanTuring's "great contribution" to Colossus (and I accept Colossus and the enigma code breakers had a key role in the Allies defeating Hitler):

"Alan Turing had nothing to do with it!"

It seemed like it wasn't the first time he had heard of Turing's "great contribution" to the engineering and practical breakthroughs that nobody now questions Tommy was crucially involved in - and he was quite keen to put the record straight!


I'm confused now. I may have mis-remembered, anyone have any sources handy?

You're not the only one who has been taught of Turing's key role in building Colossus. It just may not be completely true.

I was pretty sure I'd seen facsimilies of hardware design notes attributed to Turing, but it looks like I may be mistaken.

...Turing's "great contribution" to an engineering breakthrough... Are we talking here about the design and construction of the machine itself, or something else?

I've already asked Nic that. He would have no doubt passed the question on to Tommy (given that his main skills are political, not technical) but sadly Tommy died quite recently. But Nic was involved in arranging a special memorial service involving Tony Blair and many of the UK great and good as the government here finally owned up to Tommy's very key contribution to saving the nation - after his death.

Although Nic saw first-hand how Tommy and his wife had lived pretty much in poverty for many years, the government was apparently considering him for a knighthood the year that he died. Instead, his widow received a glowing tribute from the Prime Minister in a letter which she deeply appreciates.

There is also now a three hour video interview with Flowers in the Imperial War Museum in London in which he describes how Colossus was built and exactly how he was marginalised after the war. Once Turing was dead (some people believe he was driven to his death by the security services, who considered him a security risk), it was in the interests of such folk to build up (maybe even invent) Turing's role in building Colossus in order to deflect from Flowers as the main carrier of what were considered key military secrets by Churchill and others.

Whatever the truth, just look at the state of the UK computer industry today under the guidance of such inspired leadership ...

-- RichardDrake

This information from 'Turing's Legacy: A History of Computing at the National Physical Laboratory 1945-1995' ISBN 0 901805 94 7 (1997) by David M Yates may be helpful:

'In 1943 Colossus, an electronic apparatus to help with decryption, was designed at Bletchley Park and built for them by the post Office Research Station at Dollis Hill. The first Colossus, installed and working by December 1943, was followed by several more. Because it was programmable and electronic this system was an important step in the pre-history of computer technology, and indeed was two years ahead of its nearest American counterpart, the ENIAC.

However, Colossus was not general purpose and neither it nor ENIAC used internally stored programmes, so they could not be called computers in the modern sense. Turing took little if any part in the development of Colossus or its predecessors the Robinsons, being by then somewhat shunted off from the mainstream of cryptoanalytic work developing a system of speech encryption (Delilah).'

The above quote supports the idea that AlanTuring did not have much to do with Colossus. However, Colossus was not the only machine pitted against 'Enigma': there had been a British version of the Polish 'Bombas' devised by Turing with Gordon Welchman which was 'completed and first used in mid-1940'.

On Flowers, a footnote on p26 of the same work noting how the Post Office's contract to build the prototype ACE machine (Automatic Computing Engine, which was the brainchild of Turing) was cancelled says:

'T H Flowers of the Post Office, who during the war had led the construction of Colossus with such great success, said 'Unfortunately the pressure of telephone reconstruction after the war left so little time for other projects that eventually the commitment [to build a computer] had to be withdrawn.' '

-- MartinNoutch

As a note to the above, Colossus did not play a part in Enigma traffic de-crypt work. Colossus was used to work on Lorenz traffic, known as Tunny at BP, and was used by the German high command.

Station X - The Codebreakers of Bletchley Park, by Michael Smith has more information about the Bombes, Colossus, Enigma and Tunny, as well as the methods used.

-- Simon Culverhouse

I came across Tommy Flowers in the 1950s when I was working on the first electronic automatic error correcting system for radio telegraph links. We used the same cold cathode and dekatron circuitry as he had developed. Should he not be remembered for the first electronic telephone exchange called Highgate Wood at Muswell Hill around 1954? This, I believe, was a technical success although not a viable one at the time, as it had to be operated in a purely analogue environment.

-- Anthony Harrison

The following is taken from Tommy's obituary, published in the London Daily Telegraph on 14th November 1998:

TOMMY Flowers, who has died aged 92, built Colossus, the world's first programmable electronic computer, to help to crack Nazi Germany's most sophisticated cyphers.

The success of the Government Code and Cypher School at Bletchley Park in breaking the Enigma code is well known. Flowers was involved in a perhaps even more remarkable achievement - the breaking of the encyphered teleprinter communications used by Hitler to talk to his generals. These encyphered transmissions, known at Bletchley as Fish, were even more difficult to break, and the codebreakers attempted to use a basic computing machine known as Heath Robinson to assist in the process. Heath Robinson was a mechanical computer based on the ideas of Alan Turing, the brilliant Cambridge mathematician who played a crucial role in the breaking of Enigma. But it had a series of teething problems and, in early 1943, Turing, who was aware of Flowers's work with telephone systems for the Post Office, at Dollis Hill, suggested that he be called in.

Flowers swiftly realised that the problems with Heath Robinson could never be solved, and he made the radical proposal that the mechanical switching units, which made up the bulk of the computer, should be replaced by valves. Flowers recalled later that his suggestion was met with disbelief on the part of the codebreakers who were convinced that valves were unreliable and would keep breaking down. Flowers, though, knew from his earlier work with the Post Office that if they were never moved or switched off valves would run and run.

He succeeded in persuading the codebreakers that valves would work, but then ran into a second problem. They asked him how long it would take to produce his machine. When he told them it could be done in a year, they replied that this was no good, since by then Hitler would have won.

The codebreakers decided that they would have to continue with Heath Robinson despite its drawbacks. But Flowers was by now so convinced that his valve-built machine would work that he decided to build it anyway. He and his team at Dollis Hill constructed the first prototype in 10 months, working around the clock. Colossus, as it was to become known, was demonstrated at Bletchley Park on December 8 1943. The computer, designed to run through the many millions of possible settings for the code wheels on the German encyphered teleprinter system, was capable of processing 5,000 characters a second. But it was its accuracy in comparison with Heath Robinson that astounded the codebreakers. They set out to test it by setting up a problem to which they already knew the answer. Each run took about half an hour, and they let Colossus run for four hours. It solved the problem eight times, on each occasion coming up with exactly the same answer.

It was at once clear that Flowers's machine would be of inestimable assistance in helping the codebreakers to read communications between Berlin and all the German fronts. Perhaps more importantly, it was the first practical application of a large-scale programme-controlled computer, and as such the forerunner of post-war digital computers.

Thomas Harold Flowers was born in London on December 22 1905. After a four-year apprenticeship in mechanical engineering at the Woolwich Arsenal, he put himself through night school and earned a degree in engineering from London University. By day, he worked at the GPO's research station at Dollis Hill. It was here that he began experiments with early electronic systems that would form the basis not only for Colossus, but also for advanced long-distance telephone systems that developed into modern direct dialling.

Following the success of Colossus Mark I, the Bletchley Park codebreakers asked Flowers to build an even bigger version, with 2,500 valves rather than the 1,500 employed in the prototype. Flowers recalled that they told him the new Colossus had to be ready by June 1944 or it would not be of any use. Although the reasons for the deadline were never disclosed, he immediately realised its significance and Colossus Mark II was in place at Bletchley Park on June 1, five days before D-Day.

Colossus was constantly updated; by the end of the war there were 10 in operation, manned 24 hours a day by Wrens working to the programmes laid down by the codebreakers.

At the end of the war, all but two of the Colossi were destroyed. Flowers was ordered to destroy all evidence that they had ever existed. The two surviving machines were taken first to Eastcote, west London, the first home of the new Government Communications Headquarters, and then to its present base at Cheltenham, where a Colossus was still operational in the early 1960s.

Flowers, who returned to the Post Office to continue his work on electronic telephone systems, received a £1,000 award for his war work, barely sufficient to pay off the debts that he had run up while developing Colossus. He was also appointed MBE. But his role in the breaking of the Nazi codes and the development of the modern computer remained a secret, even to his family, for many years.

Flowers received an honorary doctorate from Newcastle University in 1977, and another from De Montfort University in Leicester.

Tommy Flowers is survived by his wife, Eileen, and their two sons.

-- Alan Blannin


Met Tommy Flowers just after his retirement from STC. This would be in 1970, and our small group of test engineers at STC was introduced to him. We had no idea of his Colossus work at the time, it still being secret.

After meeting, he walked with me to one of the production areas, and showed me a miniature strowger switch that he had worked on. About the size of a volume control in home audio. He seemed very polite and unassuming, and wanted my input on the concept! I was amazed in later years to find out about his acheivements.

In 2004 my wife and I visited Bletchley Park and saw the Colossus rebuild. I thought of Tommy Flowers back at STC in Southgate ( since closed by Nortel).

Tony Clark MIET, Ontario Canada

Back in early 1980 I had the pleasure of meeting Tommy Flowers at a meeting of retired STE (Society of Telecom Executives) engineers in London. I was a second-year apprentice with British Telecom, as it had just become, and my manager at the time had seen me reading a copy of The Secret War, the book of the BBC TV series of the late 70's which had an episode on the Bletchley Park story. He invited me to the meeting, where Tommy gave a brief talk on his part in it all. I remember him being very quiet, well-spoken and clearly very intelligent. I also remember something he said that night, which I will have to paraphrase - someone referred to him as a genius, which he disputed. He said that he thought Turing was a genius in his field, for this reason. 'You'd be working on a problem and not able to solve it, and sometimes someone would look over your shoulder and say 'Have you tried doing it like this?' and you'd think 'Of course, that's how you do it!'. With Turing, he'd say 'Have you tried doing it this way?' and you'd know that in a hundred years you would never have thought of doing it that way. And that was the difference.

I M Sheen

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