History Class, Uncategorized, World War 2

Guest Post by Mike Biles: The Ultra Enigma of Bletchley Park (Part 1)


Today I’m pleased to revisit this post from author and blogger Mike Biles. In 2019, he graciously provided two posts on the fascinating history of Bletchley Park, the headquarters of WWII code breakersSince many of you have joined me since then, he’s allowed me to give them another run. I hope you enjoy reading about this piece of history as much as I did!


This is Bletchley Park. To all intents and purposes, it’s a nondescript, somewhat ugly, large Victorian mansion and estate just north of London. But what went on at Bletchley Park was extraordinary: it changed the course of the Second World War, and the world.

From 1939-46, this was the Government Code and Cipher School (GC&CS), the place where enemy Enigma codes were broken which, as a consequence, saved countless lives and resulted in the war being shortened by at least two years. Some say. Of course, there’s far more to it than even that remarkable statement implies. Inevitably, the more you peel away the layers of the Bletchley Park legend, the more its complexities, connections and contradictions are revealed. I suspect that no one knows the full story and, probably, no one ever will.

Bletchley Park is now a thriving visitor attraction. But for years after the war, most people knew nothing about it. Renowned historians wrote entire histories of the Second World War without once referencing the vital part that Bletchley Park played. The landmark television series, ‘World at War’, first screened in 1973-74 and still remarkable viewing today, doesn’t mention Bletchley at all. It made no appearance in my edition of ‘Total War’, a recommended book on the conflict when I was a history undergraduate, despite one of its distinguished authors, Peter Calvocoressi, having served at Bletchley Park as an RAF intelligence officer.

The administration area in the mansion. Everyone’s gone home…

One of the many astonishing things about the Bletchley Park legend is that it remained a secret from the public for so long. There was an understandably obsessive sense of secrecy at the time of course, but some of the families of those that worked there never had a clue what their loved ones did. Despite the fact that ‘Station X’, as Bletchley was referred to, grew from something of a cottage industry to a huge complex that, including outstations, employed perhaps 10,000 people, everyone had signed the Official Secrets Act and most kept shtum. Careless talk costs lives; and anyway they’d given their word. The first the world at large knew of Bletchley and what happened there came in 1974 with the publication of a book, ‘The Ultra Secret’ by ex-intelligence officer F W Winterbotham. But Winterbotham’s account was nowhere near comprehensive; nor, apparently, was it wholly accurate. Bit by bit, over the years, more details have been drip-fed into the public consciousness. Some of it makes you wonder. No one should be surprised if aspects of this beguiling chapter in our history remain classified even now.

Suffice to say that to visit Bletchley Park is to take a tentative step into the shadows. We are venturing into a clandestine world, where a secret war was continuously and relentlessly waged, even when the guns were silent. What is the enemy capable of? What are his strengths, his weaknesses? What is he likely to do? When will he do it? How will he react to this, or that, circumstance? Intelligence gathering is an old craft and has many facets. One, of course, is human intelligence, or ‘HUMINT’ – the person on the ground, the spy, the James Bond or George Smiley; the mole – or the traitor. The reality of HUMINT during World War Two was all too often a dark and lonely existence far from home where, frankly, the only real success was being able to evade capture and an unpleasant death. What Bletchley dealt in was signals intelligence, or ‘SIGINT’, which rendered an infinitely more valuable product than, sadly, HUMINT ever did. The generic name used for that intelligence product was ‘ULTRA’ – because the fact that German codes were being read was more than top secret: it was ultra secret.

Notwithstanding some very public embarrassments, Britain actually has something of a reputation, dating back many centuries, in the field of espionage. During the First World War, British intelligence routinely read German military signals and code breakers working in Admiralty Room 40 decoded the famous Zimmermann Telegram which, when the contents were revealed, helped encourage the United States into the war on the Allied side. The importance of SIGINT was recognised by the establishment of the Government Code and Cipher School in 1919, though funding for intelligence in general dropped away in the 1920s – as it did again after 1945, and again in the 1990s when it was decided the Cold War had ended. This practice is called the peace dividend.

Bletchley Park was an inspired acquisition in 1938 by Admiral Sir Hugh Sinclair, the then head of the Secret Intelligence Service (‘MI6’), allegedly using some of his own money. It was handy for London, yet deemed to be a convenient distance away from anticipated German bombs. Bletchley had a station on the Varsity Line as well, the railway that ran between Oxford and Cambridge. Intelligence requires the best brains; I can’t believe I have written anything quite so profound, but do love a quote that I came across that Bletchley Park was once described as “a bad place to play chess for money.” The bulk of GC&CS (sometimes referred to as ‘the Golf Cheese and Chess Society’, incidentally) moved to Bletchley Park in August 1939 under its head, Alastair Denniston. Its official postal address was Room 47 (or Box 111, depending who you believe) at the Foreign Office. Travelling with Denniston were several cryptanalysts who had served in WW1. One of these, Dillwyn “Dilly” Knox, was a King’s College classics scholar and an expert on ancient Egyptian papyri. More Oxbridge academics were recruited, particularly mathematicians, along with linguists, chess players, lovers of crosswords – and, on the basis of trustworthiness being a matter of class and breeding, society debutantes. Personal connections and the old boy network were very important in BP’s early days. Sources of recruitment included the great London banking houses, such as Hambros and Rothschilds. Few of those taken on had a military background and some could, at best, be described as eccentric; very eccentric.

Code breaking work began in the mansion and moved as staff numbers grew: first to the garage, then cottages in the stableyard and next to hastily assembled basic wooden huts.

Restored Hut 8, where Alan Turing headed up the naval section.

Working conditions in the huts were drab and primitive, even by 1940s standards. The huts were cold and draughty with unreliable, smoky, stoves. In fact, Bletchley’s facilities as a whole were inadequate at first, and the food, whilst making allowances for the privations of wartime, was poor. From January 1942, fuel was rationed too. Work was highly compartmentalised, with different huts performing different functions. For good reasons, no one knew what anyone else was doing. Ultimately, more comfortable and solid concrete office blocks were constructed, but the insulation of different huts’ work streams continued.

Some of the derelict concrete buildings constructed to replace the wooden huts.

The scale of the task facing the Bletchley code breakers is hard to comprehend. German military signals were encrypted using the now famous Enigma machine, an electro-mechanical encryption device with a keyboard, electric plugboard and 3 independently wired rotor wheels that scrambled typed plain text into gibberish for transmission. The message could only be read by a receiving machine using the same settings. Enigma was commercially marketed to the banking sector in the 1920s, but soon adapted by the German army and eventually used by all branches of Germany’s armed services, as well as its intelligence agencies. Even the German railways used Enigma. Enigma was also bought by other nations, by the way, including the Swiss and Dutch armies. Each standard machine offered approximately 103 sextillion possible combinations using the three rotors whose settings could be, and were, changed regularly. Later German variants were supplied with 2 additional rotor wheels, which could be swapped with those in use, thus multiplying the number of available variations by a factor of ridiculous. Senior German officers were confident that Enigma made their signal traffic completely secure. At the outbreak of war in September 1939, thousands of Enigma machines were in use with Luftwaffe squadrons, Panzer units, U-boats – they were everywhere in the Third Reich, which of course came to include the greater part of Europe and wherever German forces operated. The quantity of wireless traffic was huge – thousands of messages were sent every day and they could be about anything, from procuring pencils to ordering units into position prior to launching an attack.

 An original German 3-rotor Enigma machine at Bletchley.
The rotors from an Enigma machine.

Nor was there just one code to break; the settings were different for each radio network (eg Wehrmacht, Kriegsmarine, Luftwaffe, Abwehr, Reichsbahn etc) and were changed every day. Moreover, even if a vital message were intercepted, and decoded, to be useful this had to be done before the information became out of date. Not only that, but military commanders had to first believe that the intelligence was reliable and then able to act on it. For example, ULTRA revealed the planned German invasion of Crete in 1941, but British commanders on the ground lacked the means to prevent it. Just to make things even more interesting, when codes were broken elaborate deceptions had to be employed so that the Germans did not realise that their top secret communications had been compromised. Despite some near misses, they never found out that they had been; and they never knew about Bletchley Park.

British Intelligence was of course aware of Enigma before the war and, indeed, Dilly Knox had cracked a Spanish Nationalist Enigma code during the Spanish Civil War. Later, at Bletchley, Knox’s team, lead by linguist Mavis Lever, broke the Italian Naval Enigma and then the Abwehr’s. But long before that, in 1931, a German working in the cipher office at the German defence ministry in Berlin, Hans Thilo Schmidt, began selling information about Enigma to the French Deuxième Bureau. The French eventually consulted their opposite numbers in British and Polish Intelligence. The latter had been working on Enigma for sometime. Three gifted young Polish mathematicians, Marian Rejwski, Jerzy Rózycki and Henryk Zygalski had decrypted a portion of German radio traffic and even built their own replica of a Wehrmacht Enigma machine. When it was clear that Germany would invade Poland in 1939, the Poles fully shared their secrets with the British and French. Their contribution to a common cause was vital. Rejwski, Rózycki and Zygalski managed to escape the German occupation of their country. Rejwski and Zygalski eventually made their way to Britain via France and survived the war; Rózycki drowned in 1942. Their work is belatedly recognised at Bletchley today, where there is a memorial to these barely known Polish heroes.

Memorial to the Polish codebreakers.

Breaking Enigma could never be the work of one exceptional individual. Thousands of unsung heroes and heroines worked for GC&CS during the war years. The first British cryptographer to read a German military Enigma message was an Oxford mathematician, Peter Twinn, based on the information provided by the Poles. The first wartime Enigma message wasn’t read at Bletchley until January 1940; it had been sent the previous October. Though progress was being made, the paper and pencil method of cryptography simply took too long. Among the early recruits to BP were two brilliant Cambridge mathematicians, Alan Turing and Gordon Welchman.

 Alan Turing’s modest office. Note the tea mug chained to the radiator. Alan Turing, like many of his contemporaries, was somewhat eccentric.

Turing concentrated on naval Enigma in Hut 8, allegedly because “no one else was doing anything about it and I could have it to myself.” He also produced and circulated a formal academic study on Enigma, a kind of guidebook. But Turing is probably best remembered for designing an electro-mechanical device that would mimic the workings of an Enigma and significantly reduce the time taken to run through the possible rotor combinations. This was the ‘bombe’, a name borrowed from an apparatus that the Poles developed in 1938. Turing had envisaged the concept of a computer in his 20s. He wondered whether machines could ever think – a question that he continued to ask after leaving Bletchley. But the bombe was not a computer, because it had no memory. The first one, christened ‘Victory’, was installed as early as March 1940, but had considerable teething troubles. It was Gordon Welchman who suggested an improvement which made the bombe twice as powerful, and the second bombe, ‘Agnus’ – which inevitably became ‘Agnes’, or ‘Aggie’ – was installed in August 1940. Once the bombe got into gear, it was able to test millions of possibilities – provided it was given a clue to start it off. This was called a ‘crib’. A crib is a piece of known – or guessed – text, which was used to set the wheels before the bombe was set to work. By 1945, there were 211 bombes – not all of them at Bletchley Park itself. The bombe revolutionised and accelerated the process of breaking Enigma; it was fundamental to Bletchley’s success.

A (non-functioning) reconstructed bombe. .

Most people have heard of Turing, but Welchman is less well-known. Yet, like Turing, and many others, he is an indispensible part of the Bletchley story. Welchman’s first stroke of genius was to build up a picture of enemy communications by undertaking traffic analysis – identifying who was sending what and to whom. Welchman mapped out the entire German military communication system, an invaluable piece of intelligence work, without reading a single message. Traffic analysis was the forerunner of the metadata analysis undertaken by security agencies – and commercial organisations – in today’s digital age. Welchman, who was a brilliant organiser, also saw the need to turn Bletchley Park into a factory system; the industrialisation of cryptography was largely due to his foresight.

Much of the work at Bletchley was a hard slog. Signals were intercepted at ‘Y’ stations, listening posts in the south-east and east of England, and brought to Bletchley Park by motor cycle courier at all hours. The code breakers worked round the clock, in shifts. Often, they exploited weaknesses or acts of carelessness on the part of the German senders, errors that in the cryptanalysts’ jargon were called ‘sillies’, or ‘cillis’, to give them a start. Nor was progress solely due to the efforts of staff at GC&CS. Captured rotors and documentation seized by the Royal Navy, for example, were eagerly received by the experts at Bletchley. These were instrumental in the breaking of U-boat signals, which consequently reduced the sinking of shipping and swung the Battle of the Atlantic in the Allies’ favour.

Then, in February 1942, disaster struck: the Germans introduced a fourth rotor into U-boat Enigmas and, because signals could no longer be read, shipping losses leapt upward. The breakthrough began in October when a German submarine, U-559, was attacked by a Royal Navy force in the Mediterranean and forced to surface. The surviving crew abandoned their stricken vessel under the glare of searchlights, whilst 1st Lieutenant Fasson and Able Seaman Grazier from the destroyer HMS Petard swam across to see what they could retrieve from the rapidly flooding U-boat. They were joined by a 16-year old canteen assistant, Tommy Brown. Fasson and Grazier entered U-boat and seized vital documents, which they passed to Brown, who handed them down to a whaler that had pulled alongside. These documents, particularly the latest version of a weather report codebook, provided what the code breakers needed to create cribs and were instrumental in being able to read U-boat traffic again later in the year. But Fasson and Grazier went down with the U-boat; Brown got off, but died in 1945 from injuries after rescuing his sister from a house fire.

Enigma was only part of the Bletchley Park story—

but that’s as far as today’s post will take us! Again, many thanks to Mike for all of his research, the fabulous pictures, and a look into the fascinating world of code-breaking. (Whenever I think of code breakers, I’m so thankful for people who have better math skills than I!) 

Thank you so much for stopping by today! Part II will be coming soon…


For more stories of Britain’s history and landmarks, during WWII and beyond, check out Mike’s site, “A Bit About Britain,” and his books—more below! 

Mike has lived in Britain all his life and generally loves the place, warts and all. He first learned history on his dad’s knee and went on to study medieval and modern British and European history at university. He was planning on teaching it, but then drifted into a career running his own business. Despite having worked with some of the UK’s most prestigious firms, he is often at his happiest with his nose in a history book, or exploring a historic site where the past is close. Several years ago, Mike began a blog – now an authoritative website – ‘A Bit About Britain’. He had to write a bit about Britain’s history for the website, and it seemed only sensible to put the material into his first book, ‘A Bit About Britain’s History’.

And as for Mike’s book (which I enjoyed very much!)…

Could this short, elegant, volume be the only book on British history you’ll ever need?A Bit About Britain’s History is for anyone who wants a light introduction to Britain’s amazing story. If you don’t know the basics, or would like a reminder, this book is for you. It is also perfect for those that didn’t enjoy history at school, but who have suddenly realised they’d like to understand it a bit better now. Organised clearly and chronologically, A Bit About Britain’s History covers every period from a long time ago until quite recently. It begins by briefly mentioning that the place was once inhabited by extremely large lizards, and ends up with a post-war 20th century consumer society. Short articles explain the essential aspects of Britain’s past, including how the ancestors of its current inhabitants arrived, how they fought each other, formed nations, fell out over religion, acquired a large empire, became gradually more democratic, helped win a couple of world wars and were left wondering what to do next. At the end of the book are detailed timelines for each period, which provide useful reference and make fascinating reading in their own right. So – what did the Romans achieve? How did Christianity arrive? Who are the English and why did they fight the French so often? What is Henry VIII’s greatest legacy? When did democracy start and people get the vote? Why on earth did Britain get involved in WW1?A Bit About Britain’s History might be the only book on British history you’ll ever need; or it might be your stepping stone to more in-depth academic reading.

A Bit About Britain’s History is available on Amazon, and (of course) Amazon UK.

AND, just released this year, “A Bit About Britain’s High Days and Holidays explores a baker’s dozen of Britain’s notable occasions and traditions, from New Year onward, the things we associate with them and the stories behind each one.” (To quote a piece of the Amazon blurb :))

A Bit About Britain's High Days and Holidays by [Mike Biles]

Amazon.com: A Bit About Britain’s High Days and Holidays eBook: Biles, Mike: Kindle Store

12 thoughts on “Guest Post by Mike Biles: The Ultra Enigma of Bletchley Park (Part 1)”

  1. I first came to know of this place and the extraordinary work it had contributed to the war effort was by watching the British TV series The Bletchley Circle. Then of course the movie The Imitation Game. Thanks for this is thorough and highly informative post, Anne.

    Liked by 2 people

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