Writings on technology and society from Wellington, New Zealand

Saturday, February 28, 2009

Where it all started

This week on Radio New Zealand National I talk about the Colossus computers built by the British during the second world war. They were the first computer that we would recognise today as a general data-processing machine, and to compare one with a modern server room you wouldn’t think that computers had changed that much. Apart from the rows of glowing valves and the streams of high-speed paper tape, that is.

Read on for my speaking notes or download the audio as ogg or mp3.Technology slot with Colin Jackson for Thursday 26th February 2009

But what I really want to talk about today is part of the history of computers. Last week I was broadcasting from Webstock and I was talking about the future; this week I’d to talk about the past and where a lot of the stuff we take for granted had its roots. It’s not long ago at all.

The first computer built that was anything like a modern computer was built at Bletchley Park in England as part of the World War II decoding effort. That’s the place where Alan Turing and others worked on cracking the German Enigma codes, and we’ve talked about him before. The short summary is that he was a brilliant and unconventional man whose work probably did more to win the war for the Allies than any other single person’s contribution, and that after the war he was hounded to suicide because he was gay. He has only really been recognized in the last twenty years or so.

And all this code breaking effort took place in the ground of a country house at a place called Bletchley Park, which is near Milton Keynes in the south of England. I was lucky enough to get there just before Christmas, and I saw a slightly tumble down house with some low prefab buildings around it. And an RAF Harrier jump jet parked nearby, but I’m not quite sure why. During the war there were 10,000 people working at the Government Codes and Cipher School as it was called, all in the strictest secrecy. Nobody outside the hierarchy knew this thing existed!

Q: How did they keep something that size secret?

A: I asked that. Attitudes were very different during the war. Britain was fighting for its life and people understood the value of keeping quiet about things. Loose lips sink ships and so forth. So Bletchley Park continued its work and made a huge difference to the war by decrypting German communications so the allies knew where they would be at what time.

Q: Why didn’t the Germans guess?

A: Because the allies were really careful give the German High Command other reasons for why the allies knew what was going on. They’d send up a spotter plane to where their decrypts them the Germans would be, so the spotter plane would get seen and the Germans wouldn’t be surprised. Probably the best known deception operation like that, by the way, was the so-called “Man who never was” – a corpse who had died of pneumonia, carrying documents for a synthetic identity, and purportedly top secret invasion plans, was pushed into the Mediterranean where the Germans would find it. That wasn’t anything to do with code breaking, but it was quite audacious.

Anyway, the most famous code breaking at Blethcley Park was the Enigma. But, later in the war, the Germans stated using another kind of machine as well, which they called the Lorenz machine. The British called it “fish” and they set to to break it.

Q: How?

A: They captured a lot of fish traffic over the radio, and punched it to paper tape. And they built a machine called the Colossus which they could program to look for patterns in the messages.

Now the Colossus was, well, colossal, and it had a lot of radio valves. This was in the days before transistors, so radio valves were all they had as switching elements. The first version of the Colossus add 1,500 valves, but the MkII which was the main one in use had 2,500. These things generated a lot of heat! But, then so does modern equipment.

Q: What did they look like?

A: They look strangely like racks of modern computer servers. The radio valves are all on the back so, from the front, it looks a bit like five or six computer racks bolted together. Where it differs, though, is the great paper tape loop running though pulleys at one end. That’s a long loop of paper tape running at thirty miles per hour, which is pretty quick.

Q: Did they work?

A: Oh yes. The allies were reading all the German fish traffic right through the run up to the Normandy landings and for the rest of the war. But this was held in the closest secrecy well after the war. Churchill realized that there was going to be significant tension with Russia after the war, as indeed there was. In the war’s aftermath, he told the Russians about the allies having broken the Enigma. He probably though they would have guessed anyway. But Churchill wanted the Russians never to know that the allies had broken the Lorenz machine. Perhaps he hoped that the Russians would go on using it themselves. So, Churchill ordered that all the Colossus machines be utterly destroyed – reduced to fragments no bigger than a fist. And this was done at the war’s end. Most of the buildings at Bletchley Park were taken away and it was as though the Government Codes and Cipher School had never existed.

Q: How have you seen one of these machines, then?

A: There is a reconstructed one at Bletchley Park, part of what is called the National Museum of Computing. You can go and see it. They made it out of old telephone exchange parts. Its well worth a look if you are planning a trip to the UK.


Bletchley Park, home of the British WWII code-breakers.

The National Museum of Computing, home to a reconstructed Colossus computer.

posted by colin at 2:05 am  


  1. Thank you for your interesting and accurate account of Bletchley Park.
    My friend Catherine Caughey (who died a year ago) was the first operator of COLOSSUS. I twisted her arm sufficiently that she overrode her oath of secrecy and wrote her autobiography: WORLD WANDERER, Kenya to Bletchley Park to New Zealand, Catherine M. Caughey, Auckland, 1996. That book was very favourably received, and in about 1999 Jack Perkins interviewed her on Spectrum (National Radio).
    In 2006 Oxford University Press published a major book SECRETS OF BLETCHLEY PARK (ed. by Jack Copeland), including an account by David Bolam (still living in Auckland) telling how he built COLOSSUS. And Catherine Caughey told how she operated COLOSSUS – that part was very prominently featured in reviews.

    Comment by Garry J. Tee — 26 February 2009 @ 11:51 am

  2. It really is amazing to see how far we’ve come in only 60 years. even in 40, when you think that a cellphone has many times the capability of the computers that landed Apollo on the moon. Between that and global warming, it is indeed both the best of times and the worst of times.

    Comment by Mark Harris — 26 February 2009 @ 3:22 pm

  3. “So, Churchill ordered that all the Colossus machines be utterly destroyed – reduced to fragments no bigger than a fist. ”

    Just thinking about this, if Churchill wanted the Russions to use captured Lorenz machines, why order the destruction of the only machines that could break their traffic???

    Comment by Mark Harris — 26 February 2009 @ 3:24 pm

  4. Mark

    I’m just speculating here about his motives – but he could always build more machines. The most important thing for him was that the Russians not find out that UK had been reading Lorenz and he presumably thought that there was a real risk of this post war.


    Comment by colin — 26 February 2009 @ 4:11 pm

  5. I used to walk and talk at the dog park with Mrs Caughey over the last years prior to her death. What a truly amazing woman. You talked this morning about the secrecy at Bletchley Park, well in the 25 happy years of marriage Mrs Caughey never told her husband about her participation in the programme. He passed away not knowing a thing about it. She was also required to get British Home Office permission before she could publish her book. I really miss her wonderful stories of an astonishing life.

    Comment by Christine Kirkpatrick — 26 February 2009 @ 4:33 pm

  6. After the war, GCCS became GCHQ. That’s where James Ellis worked. He came up with the idea of public-key cryptography in 1970 (five years before Whitfield Diffie), and in 1973 Clifford Cocks proved it with RSA, four years before Rivest, Shamir and Adleman thought of it.

    Of course, this was all kept absolutely top secret for years afterwards. See Simon Singh’s “The Code Book”, published in 1999.

    Comment by Lawrence D'Oliveiro — 2 March 2009 @ 7:13 pm

  7. […] Today on Radio New Zealand National at 11:05 I talk about a lot of things, but my main topic is the Rapture of the Nerds – or, rather the technological singularity (as more sober commentators describe it). Who knew that it, like so much of modern computing, came out of Bletchley Park? […]

    Pingback by » The Rapture of the Nerds — 28 May 2009 @ 9:02 am

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