Bill Tutte – Bletchley park

Thos e of you who read my articles regularly, will appreciate that I have a passion for vintage electronics, engineers who have stamped their mark on our lives and who have gone somewhat unsung. I have written about some of the heroes of the WW2 code breaking establishment Bletchley Park, Tommy Flowers and Gordon Welchman. Bill Tutte is another good example.

During the first few years of WW2, B.P. concentrated on breaking the encryption codes generated by the Enigma machine. This was used to encode the German Morse Code sent via H.F. radio. The Germans realised that using this system was a slow and a man-intensive way of communicating. At the sending end, you had the machine operator, someone to read out the message to be sent and a radio guy. A similar set up at the receiving end. 6 men all-in-all to send a message.

The German High Command, around ’41, started to use the recently invented Teleprinter machine to communicate with strategic outposts around Europe. The Teleprinter was similar to an electric typewriter. Each character, key, pressed was sent and received as a unique “set” of closely timed 5 pulses. This was known as a Baudot code. These machines could send and receive 100s of characters a minute, far quicker than Morse and using one operator. This signal was sent via a radio network to the various German Command centers around occupied Europe. Unlike Morse, each set of characters were used to frequency modulate the radio signal. Bit like our early fax machines. To scramble this signal, a machine called a Lorenz SZ40 was used. This was like an Enigma machine but on Speed and fed Cocaine.  B.P. nicknamed this Tunny. The encoded message was generated in the form of a paper strip where the holes representing the characters were punched.  A fast and very secure way of encrypting this signal. Or was it?

Bletchley Park started hearing this new radio signal and soon realized it was a sophisticated automatic system. A senior codebreaker at B.P. John Tiltman, a cipher genius, soon worked out that the transmission was encoded Teleprinter characters and was based on the Vernman cipher system. B.P had acquired a Lorenz machine, but without knowing the initial settings of the machine prior to sending a message, cracking the code was impossible. Tiltman did work out that each new message was proceeded by a 12 character set of information, details as to how to set the code of the machine for that day’s work. This tied up with the 12 encoding wheels within the Lorenz SZ40. Luck struck B.P. one day when two transmissions were intercepted, one after the other. The receiving station sent a reply message to the sender saying “Nicht bloody gut”, German for no good. The sender committed a sin which is said to have shortened the war. He resent the message, without changing the wheel settings (encryption code) on the Lorenz machine. From a mathematical point of view, this gave B.P. a huge insight as to how the Lorenz worked. This was known as a “Fish”.

The job of working out the encryption platform was given to a brilliant mathematician called Bill Tutte. Cutting a long story short, saving this magazines’ paper, Tutte visualized a reoccurring pattern in the way the scrambled message appeared. This gave him an idea that there was a flaw in the way the Lorenz worked. All he had to do now was to number crunch, broadly speaking. But this needed computer power. B.P had developed a machine called Robinson (named after the mad inventor Heath Robinson), which could be programmed to sort through and apply encryption codes to received messages. It worked by reading the paper tapes generated by the Teleprinters. However, it was unreliable, used electromechanical relays and slow for what was now required of it. Tutte started to work closely with a G.P.O engineer, Tommy Flowers (see previous article). Flowers knew the only way to create a machine fast enough and reliable enough was to use valves in place of slow relays. Tutte and Flowers had a real battle with their superiors at B.P. Flowers was told that valves were not reliable and as there was a war on, they were in short supply. This didn’t stop Flowers and Tutte. In fact Flowers spent his own money on second hand valves to create the first programmable computer (over 1500 valves in all!). Once set up with Tutte’s encryption formulas let’s say and after many hours of tweaking, Colossus as it became known, started to reliably decipher coded transmissions. By today’s standard, the machine was fast, reading paper tapes and 1000 characters a second.

The decrypted information was used carefully so as to not alert the Germans as to their High Command Teleprinter traffic being read. I guess there was a fundamental flaw the German’s thinking, in that they believed that the Lorenz machine could not be cracked. Hitler’s world did not allow free thinkers, people whose minds operated in ways that didn’t comply and so on. The sort of people that made up B.P. Hitler thought the Lorenz machine was it and that was that. I have very much over simplified this snapshot of technology!

It is said that Tutte and his team at B.P. probably shortened WW2 by 2 years, saving over 20 million souls. Were these guys ever recognized by the Great Britain? No, not really. Tutte went to work at a couple of Universities in Canada where he was recognized and received awards for advances in statistical maths. Flowers was given £1,000 to cover his cost in buying valves because funding was not available at the time. Didn’t cover the costs at all. He did get an O.B.E. and a road, in his London East End, named after him, but that was in 1990. 45 years after the war! It is awful that many of the B.P. workers struggled in later life. You were shackled by the Official Secrets Act. If you went for a job interview you couldn’t even mention the clever stuff you had done.

So I say thanks to all those at B.P. who worked behind closed doors, giving us the freedom we have today and saving countless lives. I will also thank my Granddad, George Parker. He was fireman in the war, he saved lives too! And, he enthused me in electronics.

1 thought on “Bill Tutte – Bletchley park”

  1. Hear hear, a large unsung army of heroes that, thankfully, were recognised as having a skill set they could employ to advance the war without “going to the front” and fighting. It is a scandal that so many have gone to their graves without being recognised. Some amazing stories of husbands and wives not knowing that each worked at BP during the war. Great blog SP.


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