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It shouldn't have been able to have been done - but it was!

At Bletchley Park in Buckinghamshire during World War II, mathematicians and analysts broke encrypted codes sent by the German Luftwaffe, army and navy and in doing so, both directed our war strategy and saved lives.

World War II buildings at Bletchley Park

But the country estate wasn't always a centre for undercover operations. It was owned by the wealthy 1920s financier Sir Herbert Leon, but in 1937, after both he and his wife had died, the whole estate came up for disposal as the family didn't want it. So, it was just before the war that this huge country estate of 550 acres with farms and cottages was finally broken up and put on the market.

Spotting that the site was perfectly positioned for an anonymous site north of London, the government stepped in and bought it. Communication lines were also extremely favourable. Bletchley is on the north/south railway line that runs adjacent to the site and the links between Oxford and Cambridge went through there as well. Furthermore, the nearby A5 contained all of the telecommunication equipment so Bletchley was ideally positioned as a communications centre.

At the time, Britain didn't really know if there was going to be a war or not. This site was obtained before Neville Chamberlain came back waving his piece of paper that proclaimed "peace in our time", so everything went on hold for a while. But when clearly that wasn't going to happen, the site was re-started as the satellite from London.

The important thing to remember is that it was an anonymous place, but of course, it isn't now! The important role it played during the war has gained it worldwide fame.

We spoke to Simon Greenish, the Executive Director of the Bletchley Park Trust, to fi

Can you explained what happened here in World War II?

Simon: The Enigma code machine had been adopted by the whole German military machine as their method for encoding signals. They, [the Germans] believed that this was completely unbreakable and that therefore their radio traffic was absolutely secure.

The story gets quite complex but it really started as a cottage industry, breaking the very first codes literally one at a time. But within a very short period, Alan Turing and other mathematicians had developed not only the techniques for breaking the codes as a matter of routine, but also the machinery that would help them do it.

Later on in the war they were breaking messages at a rate of over 3,000 per day which is really quite significant. This was every single day for most of that period of the war. It obviously started at less than that but, even so, right in the early days, Luftwaffe messages were being read almost as a matter of routine so it was really a very important and complex project.

So these messages came from radio waves which arrived at Y stations?

Simon: The Y stations were the receiving stations, so that all over Britain you had listening stations which tended to be around the coast. They would simply write down the gobbledy gook which would then either be sent by despatch rider to Bletchley or later on through the telephone and teleprinter system. At the peak, there were some 40 despatch riders an hour coming in here [to Bletchley] from these various stations, all feeding in this gobbledy gook which was then processed.听

Is it possible to say fairly simply how the decoding worked?

Simon: The system of communication for high speed war is radio but of course everybody can listen, so what you've got to do is to somehow encrypt the message so that you can read it but others can't. The Enigma machine was a very clever device and would take the correct German input [and change it] - so that [for] each letter [that] was fed into the machine, out would come another letter. You sent these other letters [as a message], and therefore the message was received as gobbledy gook. The receiving party had an identical machine set up to the same settings and they fed the gobbledy gook in and out came the German text.

It's a very simple system but where the complexity came in is that the Enigma machine had 158 million million million different settings on it, once the wartime additions were added to it. That's about a million million times more difficult, and with more options than if you buy one ticket for the lottery. So your chances of getting the jackpot are a million million better than your chances of finding the right settings on an Enigma machine!

But it was done?!

Simon: Yes, it was done and it was done as a matter of routine! And what's more, the settings on the Enigma machine were changed everyday so the new settings had to be found and they had to be found quickly because it's no good being able to read a message three months after you've received it. You need to read it literally within hours if you want to have any chance to use the information.

Once they'd got the mechanical devices [to read the messages], and 'The Bombe' was the prime one, they were able, through mathematical processes, to reduce the odds on the settings of the machine from a 158 million million million down to about a million. But of course that's still an unmanageable number. The Bombe machines would then take that down to about 30. Then you simply carried on testing for the 30 and so on to find the correct settings.听听听听听听听听

That is absolutely incredible!

Simon: It's an astonishing story, nothing like this had ever been done before. And the Germans believed that it was not possible to break the codes, or if it was, not in large quantities and certainly not quickly. Time and time again they looked at the evidence to see if their system been compromised and every time they said that it hadn't, when actually the evidence was very clear. If they'd looked at it properly they would have realised that it had been.

The gardens at Bletchley Park

How were the codes actually broken?

Simon: The message came in and as a raw message it wasn't decipherable. You needed to have something to help you. They knew where the messages were coming from and quite often they included something like the weather forecast, and if it's a weather forecast you can start to guess what some of [the letters and therefore settings] might be.

One of the quirks of an Enigma machine and one of its weaknesses is that it will never encrypt its own letter, so that if you press a 'P' you'll get any other letter but not 'P' so that's a starting point. So if it's a weather forecast you might guess some words in it and you might also guess Heil Hitler at the end or some other signal for standard words.

Then they started to recognise the different senders and they all had their quirks, so that gave a start, plus they made mistakes as well so that all helped. So if you thought you knew what the word is and you guessed it, then that managed to reduce the options because you knew what letter in the code could be a particular letter. That was then fed into the Bombe machine which then took the options to the next stage.听听听听听听听听

So in simplistic terms it's a bit like one of those Codebreaker puzzles, where once you've got something to give you a hook, you can slowly work out the rest.

Simon: Yes - and if you're doing it every day you soon get an idea of what these messages are, where they're coming from and who's sending them and it becomes a very repeatable process.

So what sort of people did this?

Simon: The people who actually worked on the systems for making the decoding process work were mathematicians, and other people with high levels of intellect such as chess champions. They were used to get the process working and then you also had linguists, analysts and statisticians because if you decoded a message you needed to look at it and really understand what it was saying, because the messages didn't say things obviously.

For example, they found messages saying to send lots of fuel to a place called Peenemunde up near the Baltic coast, but the question was why did they want lots of fuel up there? It didn't say 'we're building a rocket station up there - we need fuel' it just said 'send fuel'. The analysts were looking at precisely that sort of problem - they said there's something going on there we need to find out what it is.

So the messages gave the clues and then other people analysed what it might mean in a wider context?

Simon: Yes - and then other people decided whether this information needed to go directly to Churchill or to other people into a battlefield situation.

This must have saved thousands, if not millions, of lives?

Simon: Undoubtedly. I think historians, who are always cautious people in the way that they assess things, are very comfortable that the work here saved probably two years of war. It was vital in the D-Day landings because Bletchley Park was reading Hitler's personal messages through another decoding system - the Lorenz. We were reading those as well using Colossos, the world's first computer, so we were aware of exactly what the German thinking was as we were invading.

And they had no idea? It was brilliant wasn't it?!

Simon: Yes - it's probably one of the most important stories of the 20th century in Europe and indeed around the world, because what happened here set the scene for the way war is fought now.

And also it undoubtedly affected the outcome of the war which has affected how Europe is today?

Simon: Yes. And you could also go back and say what would have happened if the Battle of the Atlantic hadn't been won. Britain was facing starvation and a lack of military supplies because the Battle of the Atlantic was being lost. But it was at Bletchley that the codes for the naval Enigmas were then broken, which allowed the convoys to be routed around the submarines, so suddenly the shipping losses dropped considerably. And people argue that we would have lost the war if we'd not won the Battle of the Atlantic. So the Battle of the Atlantic was won at Bletchley Park.

So this is probably the most important place in Europe?

Simon: In a way it is. I think Bletchley Park is probably the most important site in Britain for World War II. It's the site where more important things happened and had more impact. I think the only place you could say that might be similar would be the Cabinet War Rooms where the decisions were made. But certainly in terms of war effort, what happened here had greater significance probably than any other single site.

And nobody knew?

Simon: No - even amongst the people who worked here, the process was so compartmentalised that nobody knew what was happening in the other buildings and the culture was such that you never asked.

If you talk to even the senior codebreakers who were involved at the top end and asked them if they knew how important Bletchley was, the answer would be 'no'. They knew it was important but they didn't realise how important.

And the locals in Bletchley didn't know either, they thought it was a government establishment full of boffins, which it was!

How many hours would one person work per day? Were there shifts or did they work until it was done?

Simon: There was a shift system, nobody lived on site other than the caretakers so there was a huge transport system taking at least 3000 people per shift back to wherever they lived and if you look around the site you'll see no end of bicycle shelters as well. So there was a huge logistical exercise moving people in and out.

There were eight hour shifts - three shifts per day - but if there was something exciting going on, then the people would tend to simply stay here and see it through. For example, when the Bismark was being chased around the Atlantic some people stayed here for days while that was going on.听听听听听

So, there were 3000 people being transported in and out and still nobody knew?!

Simon: No! Nobody knew!

Where did they all live?

Simon: Just in the surrounding areas. This whole area was very much involved in either codebreaking or black proaganda, spies and double crosses. There were a lot of women here as well - more women than men! They were the machine operators and did a lot of the clerical work. In fact they were doing a lot of the decoding because you still had to mechanically type in the message that you had, in order to get the German message out. Woburn Abbey was taken over by the Wrens who operated the Bombe machines here so pretty near everywhere around here in one form or another was involved. But the workers lived all over, in pubs and houses.

Presumably they were all sworn to secrecy?

Simon: They were - oh yes! Not only that, if anything started to get out you were in a lot of trouble because they recognised this was so important - it must not get out.

And there were severe penalties?

Simon: Oh yes, no question about it, and the fact is - it didn't get out and even after the war it didn't get out. That's an astonishing story in its own right. You couldn't do that again now, somebody would say something somewhere.听听听听听

And nobody knew after the war either because the government at the time, with some justification, didn't want anybody to know how successful we'd been so they simply dismantled it and closed it down. But they did take Colossos which was the next generation of even higher level code encryption and used it into the 1960s because nobody had realised that we'd broken the high grade codes. So, we were understanding what was happening in Russia in the early stages of the Cold War through the same system.

So it wasn't until the mid 1970s when people started to find out more about what happened there in the war?

Simon: Yes, in 1975 a man named Winterbottom, who had been one of the liaison officers here, wrote a book which exposed the story and it's just mushroomed from there. And there's still information coming out. As classified information is allowed out of the public records office, the story becomes more and more important.听听听听听听听听听听

What happens here now?

Simon: The story first came out in about 1975 when the site was being used by BT as a training centre. In the early 1990s, the site became available and was potentially up for redevelopment. The codebreakers met here and decided that the site was far too important for that and set about saving it. So the site is now owned by the Bletchley Park Trust and is open seven days a week as a museum. We are currently working to try and restore as much of the war time buildings as we can and each time we do one we can add to the size of the museum. What we want to do in the longer term is to fix what is a fairly rotting infrastructure, as nothing's been done here for years, but once we've put the buildings right we plan this to be an international value museum to reflect the importance of the site.

So what can people see here at the moment?

Simon: Well, it's the only site of a country mansion converted to war time use and the buildings are all still here so it's the only site where you'll actually see world War II as a site. We have a museum, we have guided tours and a visit here is certainly half a day's worth if not considerably more than that. We've also got the reconstructed Bombe which was probably one of the most important pieces of technology of World War II, and we've got Colossos the world's first computer. Both of them run, not every day, but they are working machines. We get around 60,000 visitors a year, we have a schools' education programme based around codebreaking and maths as well as history and it's a very popular site.