Read The Secrets of Station X Online
Authors: Michael Smith
The Secrets of Station X (27 page)
The station, which was staffed mainly by ATS operators, came on line in mid-1942. The German transmissions were turned into a perforated teleprinter tape. The teleprinter tape could then be fed through a teleprinter to send it to the Testery but the tapes were themselves also sent to Bletchley by dispatch rider.
Everything was done twice to ensure there were no mistakes, Kenworthy recalled.
An error in one character in several thousand was enough to cause trouble. A system was introduced to overcome this on the principle that two separate people would hardly be likely to make the same mistake. All tape was therefore measured by two girls before being read up.
The
Fish
link between Kesselring’s headquarters and Berlin, codenamed
Bream
at Bletchley, was the first of many such links that now began to produce extremely high-grade intelligence on German dispositions and intentions, and because it was at such a high level this intelligence was not just limited to the specific area covered by that particular link.
As the Germans increased the number of links and the amount of
Tunny
traffic grew, new outstations would be opened at Forest Moor, near Harrogate; Wincombe, near Shaftesbury in Dorset; Kingask, near Cupar in Scotland; and Kedlestone Hall, near Derby. The codebreakers recruited to work in the Testery included Roy Jenkins, who subsequently became Chancellor of the Exchequer and, as Lord Jenkins of Hillhead, Chancellor of Oxford University; Peter Benenson, the founder of Amnesty International; and Donald Michie, a Classics scholar from Balliol College, Oxford, who subsequently became Professor of Machine Intelligence at Edinburgh University.
Peter Hilton, later a distinguished Professor of Mathematics at the State University of New York, but brought into Bletchley Park as a 21-year-old student, was one of those working in the Testery. I was recruited by a team looking for a mathematician with a knowledge of German. I wasn’t a mathematician at the time.
I was in my fourth year at Oxford. My knowledge of German was what I had taught myself in one year so I wasn’t what they were looking for at all really. But I was the only person who turned up at the interview and they jumped at me and said: ‘Yes, you must come.’ I loved it. There is this enormous
excitement
in codebreaking that what appears to be utter gibberish really makes sense if only you have the key and I could do that sort of thing for thirty hours at a stretch and never feel tired.
Just as with the Enigma, German errors were helpful in
breaking
the system.
Sometimes the German operator made the mistake of
encyphering
two successive messages using the same wheel setting. When he did this, we could combine the two encyphered texts and what we got was a combination of the two German messages. So you had one length of gibberish which was, in
a certain sense, the sum of two pieces of German text. So you were tearing this thing apart to make the two pieces of text. And it’s absolutely a marvellous process because you would guess some word, I remember once I guessed the word ‘
Abwehr
’. So that means you have a space and then ‘
Abwehr
’, eight symbols of one of the two messages.
By subtracting the Baudot elements for those letters from the characters in the combined text, Hilton would then be left with eight letters from the other message.
But the eight letters of the other message would have a space in the middle followed by ‘
Flug
’. So then you would guess, well that’s going to be ‘
Flugzeug
’ – aircraft. So you get ‘
zeug
’ followed by a space and that gives you five more letters of the other message. So you keep extending and going backwards as well. You break in different places and try to join up but then you’re not sure if top goes with top, or top goes with bottom.
Then of course when you’ve got two messages like that, as a codebreaker, you have to take the encyphered message and the original text and add them together to get the key and then you have the wheel patterns. But for me the real
excitement
was this business of getting these two texts out of one sequence of gibberish. It was marvellous. I never met anything that was quite as exciting, especially since you knew that these were vital messages.
Throughout 1942, the work on the
Tunny
material had to be done by hand and, although some useful material was gained on the German campaign against Russia and from the links between Italy and North Africa, many of the messages took several weeks to decypher.
Max Newman, one of the mathematicians working in the Testery, was a thin, bald academic from Manchester University, who like Tutte had worked in Tiltman’s research section. He
had been Turing’s tutor at one stage. It was Newman’s
suggestion
that machines might be able to prove mathematical statements that had led Turing to write his ground-breaking paper ‘On Computable Numbers, with an Application to the
Entscheidungsproblem
’, and Newman who had ensured that it was published.
Newman became convinced that, using similar principles to those advocated by Turing, it would be possible to build a machine that, once the patterns of the wheels had been worked out in the Testery, would find the settings of the first row of wheels, thereby making the codebreakers’ task immeasurably easier.
‘Newman judged that much of the purely non-linguistic work done in the Testery could and should be mechanised and that electronic machinery would be essential,’ said Jack Good, who worked with Newman in what became known as the Newmanry. ‘He convinced Commander Edward Travis, by then the head of BP, that work on such machinery should be begun, and so the Newmanry was born.’
Newman went to Wynn-Williams at the Telecommunications Research Establishment in Malvern and asked him to design the machine. It was known as
Robinson
, after Heath Robinson, the cartoonist designer of fantastic machines, and the first version was delivered to Bletchley Park in May 1943. It worked on the principle that although the encyphering letters were supposed to be random, they were not. No machine can
generate
a truly random sequence of letters.
Robinson
compared a piece of teleprinter tape carrying the encyphered text with a piece of tape on which the wheel patterns had been punched to look for statistical evidence that would indicate what the wheelsettings were.
But while
Robinson
could clearly do its job, there were
problems
, Travis told the weekly meeting of senior staff.
Although Mr Newman’s new research machinery is still going through teething troubles, it is likely to prove better than
anything they have yet produced in the USA. The only snag is that it needs a lot of personnel. It should be able to handle 28–30
Tunny
messages a day which would be invaluable.
Robinson
was designed to keep the two paper tapes in
synchronisation
at 1,000 characters a second but at that speed the sprocket wheels kept ripping the tapes. Turing, who, while working on the Bombe, had been impressed by the abilities of a bright young telephone engineer at Dollis Hill called Tommy Flowers, suggested to Newman that he might be just the man to get
Robinson
to work.
I came into the project when the
Robinson
machine didn’t work properly, because it was made almost entirely of
telephone
parts, telephone switching parts, which was my area. I was brought in to make it work, but I very soon came to the conclusion that it would never work. It was dependent on paper tape being driven at very high speed by means of spiked wheels and the paper wouldn’t stand up to it.
Tester recalled long conversations with Flowers, Turing, Tutte and Newman over what should be done. Flowers, who had been developing telephone exchanges containing valves instead of the old fashioned relays used in
Robinson
, suggested that he could make an electronic machine built with valves that would do the same job much faster without the need for the
synchronisation
of the two tapes. The data on the wheel patterns would be generated electronically using ring circuits while the tape reading the cypher text would be read photo-electrically and could be run on smooth wheels rather than sprockets so it wouldn’t rip.
The codebreakers asked Flowers how long it would take to produce the first machine. ‘I said at least a year and they said that was terrible,’ Flowers recalled. ‘They thought in a year the war could be over and Hitler could have won it so they didn’t
take up my idea. They decided they would proceed hopefully with the
Robinson
.
I was so convinced that
Robinson
would never work that we developed the new machine on our own at Dollis Hill. We made the first prototype in ten months, working day and night, six-and-a-half days a week, twelve hours a day sometimes. We started with the design of what was to be called
Colossus
in February 1943 and we had the first prototype machine working at Bletchley Park on 8 December.
The purpose of the
Colossus
was to find out what the
positions
of the code wheels were at the beginning of the message and it did that by trying all the possible combinations and there were billions of them. It tried all the combinations, which processing at 5,000 characters a second could be done in about half an hour. So then having found the starting
positions
of the cypher wheels you could decode the message.
Flowers said the codebreakers were astounded at how reliable it was compared to
Robinson
.
What they did with
Colossus
, the first day they got it, was to put a problem on it which they knew the answer to. It took about half an hour to do the run. They let it run for about four hours, repeating the processes every half hour, and to their amazement, it gave the same answer every time. They really were amazed. It was that reliable, extremely reliable.
Colossus
was the world’s first large-scale electronic digital
computer
and as such the forerunner of the computers most people use today. It was also the first to be programmable, albeit as a result of its specialised role, semi-programmable. Although it had a specialised function, it showed the theory could be turned into practice. The sequence of operations was determined mainly by the setting of external switches and plugboards, which were
controlled by Wrens on the orders of the Newmanry
codebreakers
. Just like the
Robinson
, it was looking for sequences that were not random.
‘The work on
Tunny
divided roughly between what you might call the machine work and the hand work,’ said Peter Hilton.
Machine work was of course putting messages on to
Colossus
which was a process whereby we would determine the starting positions of the first set of five wheels which were involved in making up the key. Then after that process had taken place, that is to say a process based on statistics, mathematics, the message shorn of part of its key, would come to the
codebreakers
in the Testery who would then have the job of using their knowledge of expected pieces of text in order to set the remaining wheels.
Each codebreaker was assisted by two Wrens who set the machine up. Jean Thompson was just nineteen when she was posted to Bletchley in 1944 to work on
Colossus
.
Most of the time I was doing wheel setting, getting the
starting
positions of the wheels. There would be two Wrens on the machine and a duty officer, one of the cryptanalysts – the brains people, and the message came in on a teleprinted tape.
If the pattern of the wheels was already known you put that up at the back of the machine on a pinboard. The pins were bronze, brass or copper with two feet and there were double holes the whole way down the board for cross or dot impulses to put up the wheel pattern. Then you put the tape on round the wheels with a join in it so it formed a complete circle. You put it behind the gate of the photo-electric cell which you shut on it and, according to the length of the tape, you used so many wheels and there was one moveable one so that could get it taut.
At the front there were switches and plugs. After you’d set the thing you could do a letter count with the switches. You would make the runs for the different wheels to get the scores out which would print out on the electro-matic typewriter. We were looking for a score above the random and one that was sufficiently good, you’d hope was the correct setting. When it got tricky, the duty officer would suggest different runs to do.
Another of the Wrens working in the Newmanry was Odette Murray.
I was offered the chance of joining what was known as
Pembroke V
, not knowing what it was all about. A group of us turned up at Bletchley Park where we were taught to be touch typists, still not knowing what it was all about, and eventually I got into the park itself in the Newmanry. I was head of a watch and I was given instructions by whoever was in charge at the time and, still not having the remotest idea what I was doing, I worked with a slide rule producing a lot of figures and gave the result to the next person who gave it to the next person and eventually it was run on a tape.
Shaun Wylie had just been transferred over from Hut 8 shortly after Odette Murray arrived at Bletchley. ‘All the Wrens were swooning about Shaun Wylie,’ she recalled.
They thought he was absolutely wonderful: ‘Oh, Mr Wylie this, oh Mr Wylie that.’ I didn’t think much of him. I couldn’t see what they saw in him. However, he thought something of me.
He tried to explain to me exactly what my contribution had been in a successful thing. I just didn’t understand. I’m not a mathematician, I’m not a linguist. I’m just somebody who’s given instructions and does little funny calculations with a slide rule and bingo. A few days later a smiling Shaun comes in. I don’t know what my contribution is but okay, satisfactory.