Code-breaker clatters back to life

It was a matchless winter day, sun blazing, not a cloud over Buckinghamshire. That was the problem: after 11 years, 100,000 volunteer hours, and 2,500 scavenged valves, sunspots defeated the efforts of a re-created 1944 computer to decode a message from the German cipher machine Lorenz.

The message was transmitted from Germany every hour from 9am, and at Bletchley Park, wartime headquarters of the British code-breakers, the receiver crackled - and recorded gibberish. Only a test paper clattered around to keep Colossus warm and ready for the real thing.

"This is the very worst point in the 10-year sun cycle to have attempted this," said Tony Sale, computer boffin and former spy. "It happened often in the war, but that's no consolation. We'll get it tomorrow."

Sale led the team which not only rebuilt the Mark 2 Colossus but saved the Edwardian mansion at Bletchley Park, in which a team of eccentric geniuses found answers which modern computing would take decades to match. The messages were transmitted from a computer museum near Hamburg which has one of the German machines whose 12 wheels encoded messages from the highest Nazi command. The more famous Enigma was used for less important messages.

The Bletchley team did not know Lorenz existed, and unlike the captured Enigma, never saw one during the second world war. After they deduced its existence, and built Colossus to crack it, it is estimated the war was shortened by up to three years. In all, 10 machines were built, and from the spring of 1944 they ran 24 hours a day.

But all the machines were broken up by 1961. "We'd beaten the Germans, but there were still the Russians and the cold war was upon us. We told them about Enigma - but they never knew about Colossus," Sale said.

In 1991, he launched a campaign to save Bletchley Park, now run as a museum by a trust, and then to rebuild Colossus, which survived as a few bits of rusty metal in a near-derelict building.

The team which recreated it, working with the late Tommy Flowers, the engineer who built the first Colossus, was as eccentric as the original team. John Wetter, a retired BT engineer, says the thousands of hours he put into the project beat trailing around the supermarket after his wife. Andy Clark, director of the infant National Museum of Computing, is a professional forensic cryptographer. Sale, after a career in the RAF, worked for MI5 with Peter Wright of Spycatcher fame, before becoming a computer consultant.

Together they scavenged old parts which became redundant as BT went digital. The vital valves, replacing earlier electro-mechanical parts, are no longer made and came out of garages, attics and junkrooms.

By yesterday evening Colossus still hadn't got a complete message. Transmissions start again this morning, and the message will also go up on the National Museum of Computing website (tnmoc.co.uk) to give home cryptographers a chance. The suspicion remains that Sale knows what it is. He denies it, and you'd probably have to kill him to get it. But if you got it and he survived, he'd have to kill you: he may look like a retired bank manager, but he was after all a spy.

Backstory

In 1938, Bletchley Park, an estate near Milton Keynes, was bought by Admiral Sir Hugh Sinclair, head of MI6, and became a crucial arm of British military intelligence. A team of civilians and service personnel - all describing themselves as "house guests" and "secretarial assistants" to the outside world and joined later by American code-breakers - gradually moved into the house. Their success breaking the German Enigma machine is most famous, but creating Colossus to break Lorenz was more significant. The existence of Lorenz was deduced in 1941 when a German signalman accidentally transmitted the same message twice. Heath Robinson, named for the cartoonist's eccentric machines, was the first attempt at a code-breaking computer, followed by Colossus Mark I, operational by January 1944. By the end of the war the 10 Mark 2 models had decrypted 63m characters of German messages.