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Dr. Arnold Lynch (1914-2004)

Engineer and Scientist who made a crucial contribution to wartime code-breaking.


Until 1975 it was thought that the first fully working electronic computer had been demonstrated in the USA. ENIAC (Electronic Numerical Integrator and Computer) was announced to the world in 1946. However, in 1975 a set of captioned photographs of a secret electronic computer, built for the WW2 code-breakers at Bletchley Park in 1943, was released. This was a signal for those people who had built this computer (Colossus) and who had been sworn to secrecy, to begin to talk about this landmark development in the history of computing. One of those people was Dr. Arnold Lynch, born in Tottenham on June 3 1914.
Arnold Charles Lynch was the son of Albert John Lynch who was born at Enfield Lock in 1872. Albert trained as a teacher and after qualifying joined West Green School, Tottenham in1893. Albert was later to become the headmaster of the school. He retired as headmaster in 1934.

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Albert Lynch can be seen in the above photo at the extreme right in the back row. Seated third from the left on the bench is Thomas Edward Dent the father of Geoff Dent who found this photo. Intriguingly, Ted Willis, the playwright and creator of Dixon of Dock Green, went to West Green School and is also probably in the photo.

However, Arnold Lynch, who was about the same age as Ted Willis and Thomas Dent, doesn’t seem to have attended the school where his father taught. The Lynch family, who originally lived in Green Lanes, moved to Downhills Lane and then to a house at the top of Downhills Park Road (originally Downhill Lane).

At the outbreak of war, Albert became Mayor of Tottenham and he can be seen in the photo below, along with his wife (Arnold’s mother), reviewing the processing of “Tottenham Pudding” during a Royal visit by Queen Elizabeth (the late Queen Mother) in 1940. Albert died in 1945 and, following his death, he had a house in Bruce Grove bequeathed to the youth of Tottenham which was subsequently to become the Lynch Youth Club at Lynch House in Bruce Grove.

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At around the time of the photograph (left) , Arnold Lynch would have just begun a significant contribution to the war effort whilst he was living at Downhills Park Road. This was an optical paper tape reader which proved important in the eventual development of the Colossus code-breaking computer.


Arnold Lynch won a scholarship to Dame Alice Owen’s School in Islington in the 1920s and from there went to Emmanuel College Cambridge to study Engineering. After graduation Arnold joined the Post Office (PO) Research Centre in 1936. He was ideally placed to take on projects in electronics – a relatively new field of engineering at this time. The PO Research Centre researched and developed new technology in the field of Telecommunications.
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In the 1940s he became a member of a team of around 50 scientists, engineers and technicians working on Colossus at the Post Office Research Centre, then at Dollis Hill North West London. Some were seconded to Bletchley Park in Bucks (Station X), then the home of the Government Code and Cypher School. The Colossus project was led by Tommy Flowers, an Engineer at the PO Research Centre. The first Colossus machine operated at Dollis Hill at the end of 1943 and was transferred to Bletchley Park in early 1944. It began to carry out serious code-breaking from 5th February 1944. Many of the code-breakers at Bletchley Park had initially scoffed at the idea of Colossus. They changed their minds very rapidly when they saw what Flowers and his team, including Arnold Lynch, had achieved. It was a formidable piece of equipment at 16 feet long, 12 feet deep and 8 feet high. The name “Colossus” was well chosen. They ordered more machines and needed them fast! D Day was only a few months away.

Colossus was not developed to break Enigma as that had already been done by Alan Turing’s team at Bletchley Park. The Germans were using another code which was based on the use of teleprinters rather than Morse code used with Enigma. Fish and Tunny were the names used for these “secure” teleprinter codes used by the Nazi hierarchy. They were much more difficult to “break” than Enigma. For one thing they were more complex and the Allies did not initially know the operating principles. This was in marked contrast to the Enigma machines which were commercially available before the war. Moreover, Bletchley had an Enigma machine. Tunny machines, on the other hand, were built by the Lorenz Company in Germany at the beginning of the war; Bletchley Park did not have a Lorenz machine. Nevertheless, in January 1942, a code-breaker found a way to break into Tunny and messages could be read albeit by laborious manual work.

Unfortunately, this success was short-lived when the Germans changed the way the Lorenz machine was set up. There was a big incentive for the Allies to break the code regularly, as Tunny messages would often reveal German strategy, sometimes directly from Hitler himself.

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At this point Bill Tutte, a Cambridge mathematician working at Bletchley Park, made a major breakthrough and discovered the Lorenz cypher’s operating principles. Moreover, he found a way to decode the enciphered messages without having to investigate every possible arrangement of the “key”. Without this, a single message could have taken centuries to decipher. The partial breaking of the key was based upon mathematical principles and therefore could be “mechanised”. However, it could still take a very long time to discover the full “key” and decode the message manually as many combinations would still have to be tried. A fast decrypting machine was needed, much faster than any previous electromechanical device used for Enigma decoding.


In 1943, Tommy Flowers and Arnold Lynch became involved. Alan Turing, the most famous and tragic of the code-breakers, visited Flowers at Dollis Hill initially to discuss the use of relays in a machine to help decode Enigma. At a later time Turing suggested Flowers help with Tunny. The teleprinter based output from Tunny was in the form of paper tapes with 5 holes/no holes for the alphabetic characters and one small sprocket hole to drive the tape through the reader. The paper tapes were prepared from intercepts of the German radio teleprinter traffic by Station Y, a listening station in Kent. To decode a message in a reasonable time, a fast paper tape reader would be needed. Photo sensitive devices that detected light shining through the holes in the paper tape converted the light to electrical signals at high speed.

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Arnold Lynch already had experience with photo sensitive devices (vacuum photocells) for other projects at Dollis Hill. It therefore fell to him and his team to develop a suitable paper tape reader for this first attempt at a code-breaking machine for Tunny. Unlike Colossus, this first machine, known as Heath Robinson after the famous cartoonist of the time, was not all electronic. It had two synchronised paper tape readers: one for the encoded message and one for the assumed key text. The readers were to work at 1,000 characters per second but keeping the two tapes synchronised and also prevent them from breaking proved difficult. This machine worked in April 1943.
The Heath Robinson machine wasn’t really fast enough and it kept breaking down. Tommy Flowers suggested an alternative design to Bletchley Park; the Heath Robinson had not been his idea. Flowers removed the need for the second paper tape and used electronic valves throughout (about 1,600). This would raise the speed of the machine significantly. Most code-breakers at Bletchley Park ridiculed Flowers’ concept because they believed electronic valves (vacuum tubes) would be unreliable. Flowers knew from his experience in telephone systems, where he had used thousands of valves, that this wasn’t true. It is likely that he would have been keenly supported by Arnold Lynch in this matter if Flowers had been able to confide in him. However, it is not clear just how much Flowers could tell Lynch due to the secrecy surrounding the development.

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Although he had only limited support from Bletchley Park, Flowers received strong support from the Director of Research at Dollis Hill. In spite of the scepticism at Bletchley Park, they went ahead. Flowers now needed Arnold Lynch to improve the paper tape reader and raise its speed to 5,000 characters per second. The eventual limit to the speed was the rate at which the fragile paper tape could be passed through the reader without damage.
Speed was all important as many passes of the message tape were usually required before the partial “key” was found. In the event, the Colossus machine proved far superior to Heath Robinson in all respects. Decrypts of Tunny messages could now be obtained in a few hours. It is believed by many that Colossus brought the war to an end years earlier than would otherwise have been the case, thus saving many lives.
What happened after the end of the war is, however, something of an anti-climax. Churchill ordered that the Colossus machines should be disassembled and all paperwork and records destroyed. However, it appears that this order may not have been carried out completely. Some documents relating to Colossus have appeared in recent years. Arnold Lynch appears to have played a role in uncovering them.
Arnold Lynch returned to civilian work at Dollis Hill after the war. Before his retirement from the then Post Office in 1974 he had played the major role in the acceptance of British polyethylene over American for the first transatlantic telephone cable laid in the mid-1950s. It was just after his retirement that Cambridge University awarded him a PhD for his major contributions to Electrical Engineering throughout his career. Once retired, he pursued consultancy work with a number of engineering laboratories. At City University in London he developed electrical measurement techniques now used to meter electricity flowing in the high voltage link between the British and French national grids. At University College in London he developed innovative measurement techniques for microwave radiation. He worked at the National Physical Laboratories (NPL), where he developed methods for testing aircraft components and identifying coins in coin-operated machines. He was still working at NPL a month before he died in 2004. He received a number of prestigious awards for his engineering excellence.
It was only just after Arnold Lynch retired in 1974 that the Colossus project became widely known. Tommy Flowers was featured in a BBC programme, Secret War, in 1977 and there have been some recent BBC programmes highlighting more of the story of Colossus, the most recent of which featured a photograph of Tommy Flowers and Arnold Lynch. It is probable that yet more information will emerge in the coming years.


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In July 1994 the Bletchley Park Museum was opened and the Colossus rebuild project begun by the late Tony Sale. Arnold Lynch worked with the rebuild team to re-create the paper tape reader. The working rebuilt machine can now be seen at Bletchley Park
In recognition of his major contributions to science and technology, the Science block at Dame Alice Owen’s School, now in Potters Bar, is named the Arnold Lynch Building and his name appears in the Bletchley Park Roll of Honour.

ARTICLE WRITTEN BY:   Ray Hooper – March 2012


The following photographs were taken by Alan Swain during his visit to Bletchley Park in August 2012:


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Display Board at Bletchley Park in Recognition of Dollis Hill

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The Lost Heroes of Bletchley Park-Tommy Flowers and his Dollis Hill Team

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Display Board at Bletchley Park on the Lorenz Cipher machine

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German - Lorenz SZ42 Cipher Machine

The Colossus Machine was developed to help break the formidable 'Lorenz Code'



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Institution of Engineering and Technology (IET) Archive Department. the late Tony Sale’s web site. Bletchley Park Museum web site.

Colossus: The Secrets of Bletchley Park’s Codebreaking Computers, B. Jack Copeland. OUP 2006.
A History of Computing in the Twentieth Century: The Colossus, B Randell. Academic Press 1980.

Colossus: Bletchley Park's Greatest Secret, Paul Gannon. Paul Gannon Books

Updated : September 2012 to include Photographs taken during a visit to Bletchley Park by Alan Swain



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