It's a bouncing baby Bombe

Bletchley Park Mansion What's the connection between Mick Jagger, Stephen Hawking, three Poles and the leafy suburb of a notoriously ordered Hertfordshire conurbation? Brian Runciman, managing editor at BCS, explains.

It's not a poor joke, but rather a connection that covers one of the most important phases of World War Two; one that laid the basis for modern UK computing - the development and use of the Bombe actually an electro-mechanical computing device that was used as a code-breaker during the war, and is now entering the final phase of a rebuild project.

The Germans felt that they had unbreakable codes, produced by their Enigma cipher machines, but the pioneering work of Alan Turing with the Bombe dashed that hope.

The Bombe rebuild should be viewed as a project that maintains an important part of Britain's heritage, but it's been no easy road.

Project manager John Harper explains: 'This project has taken over ten years and we've spent £60,000, with the true value of all the support and other time spent estimated at around six times this figure as the labour has been voluntary.

'The 12 miles of cable themselves were very expensive and many of the components have had to be made from scratch, including the casting of the mechanical components and brass junctions. One of the few off the shelf items were the massive wire-wound resistors from Germany.’

The task was made more difficult due to the secrecy surrounding these machines for nearly 50 years, but the project team have now completed the rebuild and started the complex commissioning phase in preparation for the official opening by BCS in July 2007.

The project was originally sponsored by Quantel and Nortel, amongst others, but in 2001 the BCS, via the Computer Conservation Society (CCS), took a major role.

On my visit to Bletchley, the team had the Bombe running. It's loud, very loud.

'By the end of the war there were 210 of these in operation,' says Harper. 'Although the last 30 weren't used to full capacity as the war was effectively over by the time they were commissioned. They were a victim of their own success.'

The machines were run in bays of ten, so the noise must have been deafening – bearing no relation to how we work in an information environment today.

In fact there was an interesting contrast with seeing Colossus in action, as I was privileged to do, during my visit. Even with its paper tape input running it is very quiet; it must have been much more pleasant to work with.

The Bombe was the brainchild of mathematical genius’s Alan Turing and Gordon Welchman, combined with the engineering skills of the British Tabulating Machine Company in Hertfordshire.

The machines enabled Bletchley Park's cryptographers to decode over 3,000 enemy messages a day and turn the course of World War Two. Without that information the Battle of Britain and the Battle of the North Atlantic could have been lost, making a British surrender inevitable.

Filming at Bletchley

I asked John what he thought of the film Enigma, a dramatization of some of the events at Bletchley.

'Some of it was a bit silly,' he says. 'I was afraid it would upset the Poles, because it implied that they were traitors when in fact Turing couldn't have done his work without input from three Polish scientists, including Jerzy Różycki, who made a major contribution whilst still in Poland. Their contribution cannot be underestimated but sadly, for some reason, they were not allowed to work at Bletchley Park itself.

'They really got the place going by breaking the codes of the early Enigma machines - but by the time the Germans had enhanced their design it needed a lot more, which is where Turing and Gordon Welchman came in.

'Some people call the machine the Turing Bombe, but it would be more accurate to call it the Turing-Welchman Bombe because, although Turing had the initial mathematical and statistical ideas, it was Welchman who really enhanced the code-breaking power.'

There is evidence of the film all around Bletchley, from the rotting mock-up of a submarine near the Colossus building, to several Bombes made for the film - all of which feature cords instead of wires for their workings. The project team were involved as technical advisers on the movie, which is why the Bombes look so accurate.

Enter the aging Rolling Stone. Mick Jagger took one of the Bombe mock-ups for his private collection; he was a producer on the film.

In the Colossus room, Tony Sale gave me some more insight into the importance of Bletchley. By the middle of the war, the German high command had developed an even tougher cipher machine, the Lorentz, which used very different ciphers incorporating Boolean logic.

Where the Bombe had stretched electro-mechanical computing power to its very limit, Colossus was the beginning of the era of digital computing. By the end of the war, there were ten of these machines in operation and once again they had unlocked the German codes.

Interestingly, because the design of Colossus doesn't allow for stored programmes and because of its parallel processing power, the machine can still decipher codes as fast as a modern Pentium 2 PC.

So where does physicist Stephen Hawking come in?

Bletchley Park, its mansion house and surrounding huts, which date from the 1940s, also house museum exhibits, both war- and IT-related.

The actual house itself has some incredibly powerful wartime posters; building H houses a brief history of computers - from Sinclair ZX81s to Research Machine 380Zs (which I used at school); and there is also an insight into the social history of the 1940s.

There are exhibits depicting how people lived during the war including clothing, toys, radios and so on. It was here that I saw a model castle, a child's toy, which had a label informing the visitor that it had been played with by the cerebral polymath.

So what of the future for these artefacts and Bletchley itself?

With the BCS's 50th anniversary celebrations the CCS is running a special event from 12-14 July at the BCS London HQ and Bletchley Park to celebrate the achievements of UK computing during the war and the rebuild of these important devices.

In addition, BCS has just announced that it is donating £75,000 for the purpose of preserving the UK's IT history as a national asset and securing its long-term future. 

It's clearly worth it.


- Tony Sales' Colossus site
- John Harper's project page
- Bletchley Park
- Computer Conservation Society