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The Bletchley Park connection

Updated Tuesday, 23 January 2018
The once-hidden connection between Asa Briggs, Mary Siepmann, Alan Turing and many others—an estate used by British codebreakers during the Second World War.

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During the Second World War, Asa Briggs was just one of a whole generation of the brightest people in Britain (and some from Poland, France and the USA) who worked at Bletchley Park, breaking enemy codes. The process – given the codename ‘ULTRA’ – played a key role in the Allied victory. To make it work, the British government’s foreign intelligence service, MI6, recruited some of the cleverest people they could find. Because so much of the recruitment was through personal connections or Oxford and Cambridge universities, they tended to be more upper class than the population at large.

Bletchley Park Eventually, more than 10,000 code-breakers worked at Bletchley Park – where the gardens had been filled with temporary huts – or at other locations which it controlled. One thing that they all had in common was that they were all sworn to secrecy: never to talk about their work. The British realised that if their enemies knew that their codes were being broken, they would change them, and might even take steps to make the codes genuinely unbreakable. So the intelligence derived from Bletchley was only ever shared with the highest army commanders in each front.

The British secrecy held, and despite some close shaves, the German, Italian and Japanese militaries never suspected how much of their traffic was read. The Bletchley workers followed orders to keep mum after the war, too. It was not until 1975 that the UK government relented, giving Group Captain Winterbotham, the RAF intelligence officer who had helped set up ULTRA, permission to tell the truth in his memoirs.

The Bletchley connection linked many people who later gained power, prominence (and sometimes fame) in post-war Britain, particularly in academia and the law. Often, knowledge of their secret lives gives a real insight into their professional achievement. I suspect that we can trace some of Asa Briggs’ faith in the ability of an institution do amazing things back to his Bletchley days. Labour politician and Bletchley alumnus Roy Jenkins was one of the first champions of the UK’s participation in European union: he was joined in Brussels by the Conservative peer Lady Elles, who had also worked at Bletchley. Mary Siepmann worked in MI6’s codebreaking team in London and in later life found fame as the novelist Mary Wesley, whose characters were often more than they seemed.

Bletchley also played a role in the postwar development of computing, which those concerned had to keep secret. The mathematician Maxwell Newman led the design work on Bletchley’s pioneering COLOSSUS codebreaking computer, and immediately after the war he built on this expertise to help build one of the world’s first electronic computers at Manchester University. The gifted electronic engineer Tommy Flowers, who built COLOSSUS, created Britain’s most famous ‘computer’ in 1957, the random number generator ERNIE which chose the weekly winning Premium Bond numbers. The mathematician Alan Turing did brilliant and well-known work on the theory of both codebreaking and computer design. He was hounded for his homosexuality: another codebreaker, the novelist Angus Wilson, was in the 1960s one of the most prominent activists for gay rights.

The 2014 film The Imitation Game unfairly accuses Turing of being aware of spying by the USSR at Bletchley. He wasn’t: but such spying did go on. John Cairncross, who later rose to high rank in the UK intelligence services, was one of the ‘Cambridge spies’. He was later unmasked and sacked, but never prosecuted. And whatever he told his handlers about Bletchley, they kept it secret too.

In the follow audio track, I look at a key moment in code-breaking history and what it can tell us about how to treat ‘eye-witness testimony'.


Chris Williams
I’m Chris Williams, a lecturer in History at The Open University. I’m at the Bletchley Park museum, a few miles from the Open University’s headquarters in Milton Keynes. It was here, during the Second World War, that the Allies broke many crucial enemy codes, changing the course of twentieth-century history in the process. The Second World War was a radio war; and deciphering the enemy’s encrypted radio messages was a key goal for the Allies. The British high command recruited thousands of people to join the team here at Bletchley Park. They also set up secret institutions to get the resulting intelligence to commanders. The whole system was code-named ‘Ultra’, and was one of the best-kept secrets of the Second World War. From a historian’s point of view, the exposure of Ultra has been a lesson in how cautious we must be in analysing historical evidence and drawing conclusions about what happened. A good example of this point concerns the hunt for the German battleship, the Bismarck, in the North Atlantic, in 1941. I’ll be focusing on this event in today’s audio. I am standing outside Hut 8. The code-breakers worked in a number of huts like this one, specially built for the intelligence operation here at Bletchley. In this building, code-breakers worked on deciphering the messages sent from the German naval command, through the Enigma cipher called Neptune. In May 1941 they were trying to find out where in the Atlantic the German battleship Bismarck was located and, more to the point, where it was going to go next. Earlier messages, sent out by the battleship and deciphered at Bletchley, had revealed its mission: to attack British convoys in the Atlantic. I’m now going to head inside to meet Michael Kushner, one of the volunteer guides here at Bletchley. Mike, when did operations at Bletchley begin?
Michael Kushner
Well, actual operations at Bletchley temporarily began in 1938 when they were worried about a future war and they needed to purchase a new site that would be in easy reach of the big university towns of Oxford and Cambridge where they wanted to recruit their code-breakers from, their future code-breakers and they came to Bletchley and they tried it out temporarily. Then in September ’39 you had the Munich agreement when Neville Chamberlain made a last ditch attempt to make peace with Adolf Hitler and he came back waving his piece of paper saying ‘Peace in Our Time’ but the piece of paper was as shaky as the deal was and everyone knew in their hearts there was going to be a war and in August 1939 the code-breakers moved up here permanently.
Chris Williams
So how did the Enigma machine encrypt the messages sent by the enemy?
Michael Kushner
OK, so what you do is, you have a message, you type it into your Enigma machine, every time you press a key it’s changing the plain German text into cipher text, it’s changing the message completely. The difference between a code and a cipher is a code is where you change one word for another word. A cipher is where you have a word and you’re substituting letters in that word for other letters. That’s what the Enigma machine is doing. Every time you press a key it will never produce its own letter - so an A will never produce an A, a B will never produce a B.
Chris Williams
How long did it take to crack an Enigma message?
Michael Kushner
The German air force, the Luftwaffe, we were reading their codes virtually throughout the war, virtually instantaneously as we got them they could be broken, Army codes maybe a bit longer, Naval codes could be from days to weeks depending on the situation. Naval Enigma was the most difficult to break because Naval Enigma was what they called ‘super enciphered’. What they used to do with Naval Enigma was actually encipher the message before it went into the Enigma machines so it becomes super enciphered and when Alan Turing took over at Hut 8 here for his team to break Naval Enigma, he was told by Frank Birch ‘Naval Enigma is impossible to break’ and Alan Turing said ‘I like impossible tasks’.
Chris Williams
So May 1941 when the Bismarck was loose in the Atlantic, were Bletchley reading Naval Enigma?
Michael Kushner
Yes they were reading Naval Enigma , in fact one of the big hints that we got came from Luftwaffe Enigma. But we’re not too sure whether that helped us find Bismarck, we like to think it did being it came through Bletchley Park.
Chris Williams
The German battleship Bismarck was the single most powerful ship in the Atlantic in May of 1941, when it was deployed by the German navy to raid British convoys. On 24th May off Iceland, it sunk the British battlecruiser Hood and drove off the battleship Prince of Wales. The German commander Lütjens had scored a victory – but now he had three choices. He could head south into the Atlantic and attack British convoys, turn north and hide in the Arctic until the chase died down, or turn south-west to make for German-held ports in France. But he was still being shadowed by two British cruisers – the Norfolk and the Suffolk. First he had to lose them. This is what the British Admiral who was in charge of the cruisers recorded for the BBC a week later.
Archive clip: Wake-Walker
During the dark we continued to shadow her and keep touch, but unfortunately, by making a large alteration of course, she managed to give us the slip about 3 o’clock in the morning. A search was immediately started by all the ships in the area, and dispositions made by the Admiralty to cover her possible courses. As a result of this she was sighted by an aircraft of the coastal command about 10.30 on the morning of the 26th making for Brest.
Chris Williams
So, in the early hours of May the 25th, the Bismarck was lost in the Atlantic. The British Admiralty had to work out where it was and concentrate their forces against it, before it either escaped to fight again, or began destroying convoys in the mid-Atlantic. They sent out planes as well as ships to conduct reconnaissance. These are the words of one of the pilots, after he returned from his patrol on the 26th.
Archive clip: pilot
We left our base at 3.30 in the morning and we got to the area we had to search at 9.45. It was a hazy morning with poor visibility and our job was to regain contact with the Bismarck, which had been lost since early morning. About an hour later we saw a dark shape ahead in the mist. We were flying low at the time. The second pilot and I were sitting side by side and we both saw the ship at the same time. At first we could hardly believe our eyes. I believe we both shouted, ‘There she is’, or something of the sort – we were so excited that I can’t remember exactly.
Chris Williams
Once the Bismarck was found, the result was inevitable: the Royal Navy attacked with aircraft carriers, destroyers and battleships, and just a few hours after the final battle, on the morning of May the 27th, the First Lord of the Admiralty made this announcement in Parliament:
Archive clip: First Lord of the Admiralty
You will feel what I feel about their last raid and gallant sacrifice but the British Navy has in all its decades of history taken good care to avenge things of that kind and that is why this morning at 11 o’clock the Bismarck was sunk.


Chris Williams
So, the Bismarck was lost for more than 24 hours, and finding it was the key to sinking it. The question is did Bletchley find it or not? Michael, nothing was known publicly about Bletchley Park’s involvement in the sinking of the Bismarck until after the war. When did the public first get to find out about this and all the other code-breaking operations here at Bletchley?
Michael Kushner
A book was written by Group Captain Fred Winterbotham about Bletchley Park. He worked in what we call Hut 3. Now Fred Winterbotham wrote this book in 1974 and he says that the actions of Bletchley Park was a cog in the wheel of victory: an important cog because the actions of Bletchley Park reduced the war by at least two years saving countless lives.
Chris Williams
Winterbotham’s book The Ultra Secret makes references to the hunt for the Bismarck in the spring of 1941. He reports how Bletchley Park intelligence officers were decrypting messages from the ship when the Royal Navy temporarily lost it in the Atlantic. In the extract you’re about to hear, he implies that the code-breakers enabled the Royal Navy to find it again, and thus sink it.
From Winterbotham, The Ultra Secret
Early on the 25th of May Admiral Lütjens, thinking that he was still being shadowed by a British warship, sent a long signal to his Naval Headquarters in Germany. It listed all the difficulties but mainly the loss of fuel from his earlier battle and he asked what he was to do now. It was this signal, picked up by us, which gave away once more his position. I remember the thrill that went through the office as the next signal came over the telephone from Hut 3 that Bismarck had been ordered to go to Brest where all available air and submarine protection was to be given to her.
Chris Williams
Derek Taunt, a Cambridge University student and Bletchley code-breaker, also believed that the information provided by Bletchley Park to the Admiralty enabled the navy to find and sink the Bismarck. This is an extract from his account, published in 1993.
Derek Taunt
An example of a prime snippet of secret knowledge which we had to keep to ourselves concerned the Bismarck, which had been sunk some three months before my arrival in Hut 6. I was told that its whereabouts at a critical moment had been revealed in an Enigma message to a high-ranking German Air Force officer, whose son was aboard the doomed ship. Thus our success in reading Red, the main German Air Force key, had played an important part in this drama.
Chris Williams
This account by Taunt reveals the common belief amongst Bletchley code-breakers that Bletchley Park had played a key role in the navy’s success. Bletchley Park typist Betty Hutchinson also had no doubt that the code-breakers had been instrumental in the sinking of the Bismarck. She was interviewed by the BBC in February of 1977.
Archive clip: Betty Hutchinson
Of course, we tracked the Bismarck the whole way until our navy got her.
Chris Williams
But it’s important to note that at the beginning of 1977 the documents relating to Bletchley Park had yet to be released to the Public Records Office. Witnesses who had worked at Bletchley were therefore telling the story from memory alone. In a radio broadcast in January of the same year, Peter Calvocoressi, one of the senior intelligence officers who had worked at Bletchley Park, reported his experiences but acknowledged the incomplete nature of his evidence.
Archive clip: Peter Calvocoressi
The things I’ve been talking about have been successfully kept secret for an astonishing number of years. And most of them still are. No documents have been released for public inspection and I’m told none will be until the 80s. I myself have had access to no such documents since the war. When I first went to Bletchley I was in my twenties and that’s a good time ago. Memory is an uncertain guide. So what I have to say can be no more than an interim assessment to be checked and no doubt modified when the records become available. On the other hand, I was there for much of the war, and I have recently refreshed my memory by talking to others who were there too. Though still others, with valuable testimony to give, have died.
Chris Williams
Winterbotham was also interviewed by the BBC in 1977 and admitted that the role of Bletchley Park in winning the war could not be stated with certainty.
Archive clip: Winterbotham
I don’t think that any general or army, before or since or in the future, is ever likely to be in a position of knowing exactly what his enemy’s going to do. I think history will have to decide what role Ultra really played. I’m a little prejudiced myself – I think it did a great deal.
Chris Williams
In this clip, Winterbotham describes himself as ‘prejudiced’. Like Peter Calvocoressi, he admits his account of the role played by Bletchley Park is not necessarily wholly trustworthy. Other sources, he implies, might challenge his assessment. And so they did. Here in front of me I’ve got a book, first published in 1978 called Ultra Goes to War. In it, Ronald Lewin argues that Bletchley Park wasn’t responsible for actually sinking the Bismarck: by the time the messages were decrypted, the Admiralty had already worked out where it was and deployed the planes which found it.
From Ronald Lewin, Ultra Goes to War
In that month of May, and for many years afterwards, there were those who felt that Ultra had made a contribution which was even thought to have been decisive. At Bletchley this view was widespread. And yet on investigation it proved difficult to pinpoint any moment when Ultra could in fact have affected the issue. This is certainly the considered opinion of Admiral Sir Norman Denning and Patrick Beasley who were on duty at the Admiralty’s operational intelligence centre during the battle, took note of all the incoming information and observed from hour to hour the many dispositions of ships and aircraft that in the end brought Bismarck to bay. A reconciliation is necessary between appearance and reality.
Chris Williams
After 1945, many of the people with interesting experiences of the war recorded their recollections. But some people – even those who’d been in the middle of events – came away with an inaccurate sense of the significance of what they’d seen. Events are easy to notice – it’s the causes of events that’s often trickier to interpret. The Bismarck was sunk, and the staff at Bletchley thought that they had made this happen. They were all subject to extreme secrecy requirements, and so more likely to accept this widespread rumour than to question it. The key piece of evidence was the hourly intelligence summary, which showed exactly what the Admiralty knew and when. As we just heard, Ronald Lewin used this evidence in his analysis. He concluded that Bletchley Park was in fact too late in decoding the messages, which identified the Bismarck’s course. Winterbotham knew about the decrypts he passed to the Admiralty, but he didn't know about the other sources of information the Admiralty were also using. The lesson to be learned is that the phrase ‘I was there’ doesn’t always mean that the witness can explain the cause of an event. Looking in the archives, bringing different people’s recollections together, can confirm that some myths reflected reality, but others – like ‘Bletchley sank the Bismarck’ – don’t hold up.

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