DOLLIS HILL'S FINEST

 

See Also: COMPUTERS The Post Office Research Station; THE SECOND WORLD WAR

The Government Code & Cypher School had been founded following the First World War. It had been created through the merger of the Army and the Navy's code-breaking sections. At the suggestion of the 1st Marquis Curzon, the new entity had been placed under the supervision of the Foreign Office. Following the outbreak of the Second World War, it was expanded rapidly. Many of its new staff were seconded academics. They brought to it an array of new analytical techniques. Its activities were carried out principally at Bletchley Park in Buckinghamshire.

The code that the German Army used to transmit radio messages from one teleprinter to another was dubbed Tunny by the Bletchley code-breakers. In 1941 a German soldier made the mistake of retransmitting a message that he had just sent. This provided a chink in the cypher's armour. The cryptanalyst John Tiltman proved to be able to crack it. However, the prolonged nature of his doing so by hand meant that only a miniscule portion of the intercepted communications traffic could be understood.

The mathematician Max Newman argued that the process could be automated. He set down a specification for a machine to do so. At the time, the Post Office ran Britain's telephone network. The expertise of its research station in Dollis Hill was called upon. The engineer Frank Morrell led the construction of an eccentric-looking, switch-based device. Those who contributed ideas towards its creation included his colleague Tommy Flowers and Charles Eryl Wynn-Williams of the Telecommunications Research Establishment. The wrens who operated the apparatus dubbed it Heath Robinson in honour of the illustrator W. Heath Robinson, who specialised in drawing elaborate, imaginary machines. However, the volume of coded material was so great that it was unable to keep abreast of it.

Through needing a decoding machine to help break the Enigma cypher, Turing had come to know Flowers. He recommended to Newman that the man should be invited to address the problem. The engineer concluded that there was scope for building a piece of equipment that utilised thermionic valves (vacuum tubes). He had used them to create the repeaters that were central to the operation of the Post Office's telephone system and he knew that they were reliable just so long as they were kept switched on permanently.

The components for the 1500-valve prototype were built and assembled at Dollis Hill. The parts were taken to Bletchley, where the machine was constructed at the end of the year. It was able to use binary logic to do huge calculations. The device had no internal memory. Therefore, it had to be reprogrammed for each run. Its large size led to it being called Colossus. The device sped up the deciphering of the Lorenz code from days to minutes.

The 2400-valve Colossus Mark II started running in mid-1944. By the end of the war there were eleven machines in operation. Following the return of peace, the School was renamed Government Communications (G.C.H.Q.) and vacated its Bletchley site. Two of the devices accompanied it. Churchill ordered that the other nine should be destroyed along with the plans that had been used to build them. The Cheltenham pair are believed to have been operated until 1958. They are thought to have then been dismantled.

Tony Sale had a working life that was largely focused upon computers. For a period, he was employed by Marconi at its Great Baddow research laboratories in Chelmsford. There, his boss was one Peter Wright. The latter was recruited by M.I.5 to work on radio interception and the placement of bugging devices. Mr Sale followed him into the service. Within it, he became a principal scientific officer.

In the early 1990s Mr Sale was running the Science Museum's Computer Restoration Project. He saw a set of eight wartime photographs of a Colossus. Although this was all the evidence that was then available to him, he became convinced that he could build a version of the machine. Top-level security clearance was conferred upon him. He then embarked upon a programme of interviewing the surviving project engineers. Their number included Flowers. One of them had a notebook that contained ten fragments of a circuit diagram.

The curator's task benefitted from the fact that the machines had been assembled in large part from the standard telephone exchange gear that had been at hand at Dollis Hill. In the 1990s the United Kingdom's telecommunications infrastructure was being updated. Therefore, he was able to purchase many of the components as scrap. The United States Freedom of Information Act allowed a major breakthrough to occur in 1995. The measure enabled a technical description of Colossus to be unearthed. This had been written in the 1940s by a visiting American scientist.

Sale founded the National Museum of Computing, which is based in Bletchley Park. In 2007 it became the home of his recreated Colossus. When this was run for the first time, it proved to be able to crack a message that had been encrypted in the Lorenz cypher.

Location: The Science Museum, Exhibition Road, SW7 2DD (red, turquoise)

Chartwell Court, Dollis Hill, 151 Brook Road, Dollis Hill, NW2 7DW

Website: http://bletchleypark.org.uk (Bletchley Park Trust) www.computerconservationsociety.org (The Computer Conservation Society) www.tnmoc.org (The National Museum of Computing) https://collection.sciencemuseumgroup.org.uk/collection/cp38152/post-office-engineering-research-station (The Science Museum)

David Backhouse 2024