Bletchley Park - Mansion

Bletchley Park - Mansion

Bletchley Park Stableyard Cottages

Bletchley Park Stableyard Cottages

Bletchley Park is opposite Bletchley railway station. The site appears in the Domesday Book as part of the Manor of Eaton. Browne Willis built a mansion there in 1711, but after Thomas Harrison purchased the property in 1793 this was pulled down. It was first known as Bletchley Park after its purchase by Samuel Lipscomb Seckham in 1877. The estate of 581 acres was bought in 1883 by Sir Herbert Samuel Leon, who expanded the then-existing farmhouse into the present "maudlin and monstrous pile" combining Victorian Gothic, Tudor, and Dutch Baroque styles. In 1938, the mansion and much of the site was bought by a builder planning a housing estate, but in May 1938 Admiral Sir Hugh Sinclair, head of the Secret Intelligence Service (SIS or MI6), bought the mansion and 58 acres for use by GC&CS and SIS in the event of war.


The arrival of ‘Captain Ridley's Shooting Party’ at a mansion house in the Buckinghamshire countryside in late August 1938 was to set the scene for one of the most remarkable stories of World War Two. They had an air of friends enjoying a relaxed weekend together at a country house. They even brought with them one of the best chefs at the Savoy Hotel to cook their food. But the small group of people who turned up at Bletchley Park were far from relaxed. They were members of MI6, and the Government Code and Cypher School (GC&CS), a secret team of individuals including a number of scholars turned Codebreakers. Their job; to see whether Bletchley Park would work as a wartime location, well away from London, for intelligence activity by GC&CS as well as elements of MI6.


The GC&CS mission was to crack the Nazi codes and ciphers. The most famous of the cipher systems to be broken at Bletchley Park was the Enigma. There were also a large number of lower-level German systems to break as well as those of Hitler's allies. At the start of the war in September 1939 the codebreakers returned to Bletchey Park to begin their war-winning work in earnest.


The Poles had broken Enigma in 1932, when the encoding machine was undergoing trials with the German Army. But when the Poles broke Enigma, the cipher altered only once every few months. With the advent of war, it changed at least once a day, giving 159 million million million possible settings to choose from. The Poles decided to inform the British in July 1939 once they needed help to break Enigma and with invasion of Poland imminent. As more and more people arrived to join the codebreaking operations, the various sections began to move into large pre-fabricated wooden huts set up on the lawns of the Park. For security reasons, the various sections were known only by their hut numbers.


The first operational break into Enigma came around the 23 January 1940, when the team working under Dilly Knox, with the mathematicians John Jeffreys, Peter Twinn and Alan Turing, unravelled the German Army administrative key that became known at Bletchley Park as ‘The Green’. Encouraged by this success, the Codebreakers managed to crack the ‘Red’ key used by the Luftwaffe liaison officers co-ordinating air support for army units. Gordon Welchman, soon to become head of the Army and Air Force section, devised a system whereby his Codebreakers were supported by other staff based in a neighbouring hut, who turned the deciphered messages into intelligence reports.


Bletchley Park - Hut 1

Bletchley Park - Hut 1

Bletchley Park Hut 4

Hut 4 Bletchley Park

Secrecy shrouded the fact that Enigma had been broken. To hide this information, the reports were given the appearance of coming from an MI6 spy, codenamed Boniface, with a network of imaginary agents inside Germany. While this was pure fiction, there was a real network monitoring the Germans’ every move. The ‘Y’ Service, a chain of wireless intercept stations across Britain and in a number of countries overseas, listened in to the enemy's radio messages. Thousands of wireless operators, many of them civilians but also Wrens, WAAF personnel and members of the ATS, tracked the enemy radio nets up and down the dial, carefully logging every letter or figure. The messages were then sent back to Bletchley Park (Station X) to be deciphered, translated and fitted together like a gigantic jigsaw puzzle to produce as complete a picture as possible of what the enemy was doing. The Codebreakers began working around the clock to send the intelligence they were producing to London. Special Liaison Units and their associated communications specialists, the Special Communication Units, were set up to feed the Bletchley Park intelligence to commanders in the field, first briefly in France in May 1940 and then in North Africa and elsewhere from March 1941 onwards.


The process of breaking Enigma was aided considerably by a complex electro-mechanical device, designed by Alan Turing and Gordon Welchman. The Bombe, as it was called, ran through all the possible Enigma wheel configurations in order to reduce the possible number of settings in use to a manageable number for further hand testing. The Bombes were operated by Wrens, many of whom lived in requisitioned country houses such as Woburn Abbey. The work they did in speeding up the codebreaking process was indispensable. In October 1941 after receiving a letter from some of the senior codebreakers decrying the lack of resources being afforded them, Prime Minister Winston Churchill directed: ‘Make sure they have all they want extreme priority and report to me that this has been done.’ From that moment on Bletchley Park began receiving a huge influx of resources and a major building programme ensued to create the space necessary to house the ever increasing workforce.


The intelligence produced by deciphering the Naval Enigma was passed to the Admiralty via the Z Watch in the Naval Section. However, in the early days, they struggled to get the naval commanders to take it seriously but a series of spectacular successes turned things around for the Codebreakers. Throughout the First Battle of the Atlantic, they helped the Admiralty to track the U-Boat wolf packs, considerably reducing the German Navy's ability to sink the merchant navy ships bringing vital supplies to Britain from America. Nor were the Germans the only targets for Station X - by breaking Japanese ciphers, the Codebreakers were able to monitor the Japanese preparations for war. The suggestion that they knew of the imminent attack on Pearl Harbor but kept quiet in order to ensure America joined the war is nonsense. But their expertise undoubtedly gave great assistance to the American codebreakers. In 1942, the Codebreakers' many successes also included the North Africa Campaign, when they enabled the Royal Navy to cut Rommel's supply lines and kept Montgomery informed of the Desert Fox's every move. Early 1942 brought serious difficulties with the German Navy’s introduction of a more complex Enigma cipher. But by the end of 1942 they had mastered it as well.


Perhaps Bletchley Park's greatest success was still to come with the breaking of the Germans' strategic ciphers. These complex ciphers were used to secure communications between Hitler in Berlin and his army commanders in the field. The intelligence value of breaking into these was immense. Initial efforts were manual and successful, but could not keep up with the volume of intercepts. Under Professor Max Newman the ‘Newmanry’ started to devise machines to mechanise the process. This ultimately led to the design and construction by the brilliant General Post Office (GPO) engineer Tommy Flowers of ‘Colossus’, the world's first semi-programmable electronic computer. Breaking into these ciphers allowed the Allied staff planning for the invasion of Europe to obtain unprecedented detail of the German defences.


The Codebreakers made a vital contribution to D-Day in other ways. The breaking of the ciphers of the German Secret Intelligence Service allowed the British to confuse Hitler over where the Allies were to land. His decision to divert troops away from the Normandy beaches undoubtedly ensured the invasion's success. But even as the Allied troops waded ashore, a new threat was looming and attention was being given to the role of the Codebreakers in the post-war era. In January 1945, at the peak of codebreaking efforts, some 10,000 personnel were working at Bletchley and its outstations. A substantial percentage of personnel at Bletchley Park, 75%, were women; among them were Mavis Batey and Margaret Rock, who were credited for the Abwehr break. Their work achieved official recognition only in 2009. Many of the women came from middle-class backgrounds and held degrees in the areas of mathematics, physics and engineering; they were given entry into STEM programs due to the lack of men, who had been sent to war. They performed complex calculation and coding and hence were integral to the computing processes - Jennifer S. Light writes that the Women were indeed the first computers.


With the declaration of peace, the frenzy of Codebreaking activity ceased. The thousands who had worked at Bletchley Park departed. Some continued to use their remarkable expertise to break other countries' ciphers, working under a new name: the Government Communications Headquarters (GCHQ). As World War Two gave way to the Cold War, it was vital that Britain's former ally, the USSR, should learn nothing of Bletchley Park's wartime achievements. For decades, those involved with wartime Bletchley Park would remain silent about those achievements. In 1974 FW Winterbotham, who had worked on Ultra at wartime Bletchley Park, published a book called ‘The Ultra Secret’; an extensive, although at times inaccurate, account of the work and accomplishments of the Codebreaking hub. So the secret was out and the ban on talking about it was lifted although detail about ‘Britain’s Best Kept Secret’ emerged only gradually and sporadically over the years that followed.


Bletchley Park boasts a Visitor Centre, restored buildings and exhibits to preserve and commemorate the tireless work of the Codebreakers. Highly atmospheric soundscapes play snatches of conversation, music, laughter and even a hint of romance, as well as the noises of bicycle bells and steam trains to conjure up how it would have sounded to work alongside a cast of thousands at wartime Bletchley Park. Having already enjoyed the overview exhibition visitors can experience a nostalgic sense of place and history in the country estate setting the Codebreakers cherished.


The Museum has step free access. All the exhibitions are positioned at ground floor level bar one, Block B, which has a wheel chair lift. Ramps are installed on site for easy access. There are 12 disabled parking spaces at the back of the porters lodge at the entrance and another 5 in Block F car park. Wheelchairs are available to borrow at the entrance for your visit. Unfortunately the Museum cannot provide assistance around the Museum for wheelchair users. However assistance will be available at wheelchair lifts. BSL interpreted guided tours are available throughout the year. Guide and assistance dogs are welcome. Dog bowls are available from the admission desk. Sound enhance systems for both hearing aid users and non hearing aid users are available for the 12.00 tour and the 14.00 tour. Please arrive 10 minutes before your tour is due to start and speak to your friendly tour guide who will provide you with the equipment. The necessary escort of a visitor with a disability is admitted free of charge upon request, while the normal charge applies to the disabled visitor. Admission includes complimentary use of the Multimedia Guide plus an optional 1 hour, outdoor walking tour with a tour guide, subject to availability.

Rebuilt bombe

Rebuilt Bombe

Mark 2 Colossus computer

Mark 2 Colossus computer

National Museum of Computing



The National Museum of Computing is a museum in the United Kingdom dedicated to collecting and restoring historic computer systems. The museum is based at Bletchley Park in Milton Keynes, Buckinghamshire and opened in 2007. The building — Block H — was the first purpose-built computer centre in the world, hosting six Colossus computers by the end of World War II. Colossus, the world's first electronic computer, had a single purpose: to help decipher the Lorenz-encrypted (Tunny) messages between Hitler and his generals during World War II. The Colossus Gallery housing the rebuild of Colossus tells that remarkable story. Colossus reduced the time to work out the Lorenz chi-wheel settings and enabled more messages to be deciphered and the whole code-breaking operation to be accelerated. The information gleaned from the decrypted messages is widely acknowledged to have shortened the war by many months, saving tens of thousands of lives. The cipher text was input via paper tape and the 2500 valves of Colossus would find the Lorenz machine chi-wheel settings. By the end of the war, 63 million characters of high-grade German communications had been decrypted by 550 people helped by the ten Colossus computers.


The Tunny Gallery, along with the Colossus Gallery, shows the entire World War II code-breaking process of the Lorenz-encrypted messages (known as Tunny in the UK) from encrypt in German-occupied territories to signal intercept at the Knockholt receiving station in Kent to the production of the final decrypts on Tunny machines in Bletchley Park. German High Command communicated across about 20 links in German-occupied territories in Europe using a Lorenz encrypting machine. It is estimated that about 200 Lorenz machines were in existence during World War II, but only four are known to have survived. The Lorenz SZ42 machine displayed at TNMOC has the serial number 1137 and was used at the German HQ in Norway at Lillehammer, north of Oslo. Since Norway was occupied by the Germans until the end of the war, we believe it will have received the final surrender instruction message at 24:00 hrs on 8 May 1945, marking the end of the war. Alongside the Lorenz is an original Spruchtafel, the Lorenz wheel-setting aid. It is one of only two thought to be in existence today. The original Tunny machine, a re-engineering of the then unseen Lorenz SZ42 cipher machine, was designed by the Post Office Research Station in 1942. It produced the final decrypts of enciphered teleprinter communications of the German High Command during World War II.


In the largest gallery in the museum, you can see just how big those early systems really were. There's the Harwell Dekatron aka WITCH computer from the early 1950s and the ongoing reconstruction of EDSAC that dates back to 1949. Whenever families with children visit, they are always amazed just how big the systems from the 50s, 60s and 70s really were. Their only knowledge of computing might be the PC or laptop they have at home, or the iPod and mp3 player in their pocket (which has many times more processing power than all the systems on display). In 1949 plans were drawn up for a machine to automate the tedious work performed by teams of bright young graduates using mechanical calculators. Simplicity, reliability and unattended operation were the design priorities. Speed was of a lower priority. This pioneering computer first ran in 1951 and by 1952 was using 738 Dekatron tubes for program and data storage, relays for sequence control and valve-based electronics for calculations. It was used at Harwell until 1957, when it was won by Wolverhampton and Staffordshire Technical College (later becoming Wolverhampton University) in a competition for colleges to see who could make best use of it. It then became known as the WITCH (Wolverhampton Instrument for Teaching Computation from Harwell), and was used in computer education right up until 1973. After a period on display at Birmingham Museum of Science and Industry, the computer was disassembled and stored at Birmingham City Council Museums’ Collection Centre. In 2009 the machine was spotted dismantled in storage by TNMOC volunteers and a plan was made to bring it to TNMOC for restoration in full public view. A tortoise not a hare; the Harwell computer was pitched against a human mathematician to check the machine’s operation. The human kept pace for 30 minutes, but then retired exhausted as the machine carried on remorselessly. The computer once ran unattended for ten days over a Christmas/New Year holiday period.


TAC - Transistorised Automatic Computer. Dating to around 1958/60. this is one of the more unusual systems we have on display. Contained within four large cabinets and a control desk, it was one of the first transistorised computers made in the UK. This one was used as a monitoring system for a nuclear power station. It gave sterling service for many years from its installation in the early 1960s to finally being decommissioned in 2004 - that's over 40 years! That is amazing considering the technology being used. Elliott 803B. This is a fully functioning machine from around 1962 which, when it was donated to the museum, had spent about 15 years in a farm barn. The restoration was lead by John Sinclair, and the machine has been running with little need for attention for many years. It has recently had two upgrades: The addition of a Calcomp drum plotter and some additional input/output features. As well as the system on display here at TNMOC, John has also restored and maintained an 803B system for the Science Museum in London. As with any good system we have it working hard each Saturday. Members of the project team keep their programming skills sharp by developing programs for the 803 using the original software tools. These programs play music, draw graphs or solve mathematical problems. One recent program calculates the cost of a shopping list in pounds, shillings and pence (£sd, the UK's currency pre-decimalisation in 1971). This is a far cry from its original use for planning bakery delivery routes or accounting, but it does allow the system to be shown working and in doing so ensures its continued operation. Two fully operational Elliott machines; 803B and 903 are on display at TNMOC. IBM 1130. The IBM 1130 was launched in 1965 and was the first system IBM designed to work in an office environment. It was still in use in the early 1980s with over 10,000 systems believed to have been built during a working life spanning nearly 20 years. As well as being used in small to medium sized offices, it was also used extensively in colleges and universities for both scientific and 'office' roles. The one currently running at TNMOC came from Liverpool university and is on a long-term loan, and according to some paperwork found with the system, it was used in the Nuclear Physics department. It is one of only 4 known working examples in the world, with 1 in Germany and 2 in the USA.


The PC Gallery with desktops from the 1970s to the present is a real favourite with visitors and a trip down memory lane for many. Nostalgic for some, it's a real eye-opener and a favourite for students on educational trips. Innovative designs such as BBC Micro, Sinclairs, Amstrads and others from Europe and the USA, many of them working, are on display to trace the development of personal computing from the 1970s. The Gallery also has timelines of the development of hardware and operating systems as well as a timeline of computing set in the context of world events, politics, culture and science. Did you know that our very own BBC (yes that's the British Broadcasting Corporation) was instrumental in commissioning mass-market computers in the early 1980s? Probably one of the most iconic home computers of the eighties, the BBC Micro found its way into the homes of over 1.5 million people by the time it ceased production in 1986. Starting out as an educational tool for the BBC Computer Literacy Project, it soon evolved into a popular games machine (Elite anyone?), allowing you to build and control a wheeled mouse, to being a fully fledged Domesday laser disk archive system. It is also reported that as late as 2004, a BBC Micro was still being used to steer the 42ft radio telescope at Jodrell Bank. It found more uses than probably any other system of its time and many a computer programmer of today started with BBC Basic.


Long before electronic computers became available, many offices were already mechanised and used sophisticated punched card machines for the production of payroll, accounts, and stock control. Highly trained operators punched data on the cards that could be repeatedly sorted and used to produce reports. A typical office suite would consist of a punch, a sorter, a collator, and a tabulator. In payroll, for example, the card was punched with the employee number, the total hours worked and their hourly rate. The Electronic Multiplying Punch (EMP) would then calculate the total pay and punch it back onto the same card. The cards were mechanically sorted into employee number and payslips then printed by the tabulator. The stacks of cards were carried from machine to machine by operators, who carefully avoided dropping them! TNMOC’s punched card equipment display is a suite of machines produced by the British company Powers-Samas. Part of it was used by Blackpool Corporation in its transport department in the 1960s for wages, stores and mileage records. Using cards with 40 columns rather than the more standard 80 columns, it was programmed using hard-wired program boards and required eight machine operators to punch the cards and produce the reports.


For centuries before computers were invented, calculations could be performed on some ingenious and beautifully designed devices. An Abacus, slide rules, calculators of all shapes and sizes are on display and may even be remembered by some visitors. The Museum has the largest display of slide rules in the UK, courtesy of the UK Slide Rule Circle. Forty different slide rules show the development of these devices over four centuries. Invented in the 1620s soon after the publication of concept of the logarithm, slide rules were in use right up to the 1980s although their decline began in the 1960s with the advent of electronic calculators and computers. Popular with the taxman across the centuries for calculating the volume of spirits in barrels, slide rules come in all shapes and sizes. There is even one on display that can calculate the amount of meat on a cow! The mechanical adding machine was invented in the seventeenth century, the familiar push button machine arrived in the twentieth century and in the 1950s transistor technology enabled the development of fully electronic calculators. By the 1970s, they had become pocket-sized. The Museum has an array of calculators from across the years.


In addition there are galleries dedicated to Women in Computing, the Software Gallery, Air Traffic Control, the NPL Internet Gallery and Analogue Computing. The museum has wheelchair access to all galleries and displays. Assistance dogs are welcome. There is a unisex disabled toilet near the TNMOC Shop. There is a coffee and souvenir shop. The public guided tours are very popular and enable visitors to see the collection on days when the Museum is busy with educational and other groups. To book a place on a tour: you can book in advance online or buy a ticket as soon as you arrive at Block H (The National Museum of Computing) on Bletchley Park. Places are limited to 16 people, so on-line advance booking is recommended. The cost is £12.50 (concessions £10). The Tour lasts about 2 hours and covers the full museum collection from Colossus onwards. Much of what is on display actually works, and the guides describe how the computers were used, tell anecdotes on their design and operation, and operate some of the equipment.


Location : The Mansion, Bletchley Park, Sherwood Drive, Bletchley, Milton Keynes, MK3 6EB

Location : The National Museum of Computing, Block H, Bletchley Park, Milton Keynes, MK3 6EB

Transport : Bletchley Park (National Rail) 100 yards. Bus Routes : 1, 24 and 25 stop close by.

Opening Times Bletchley Park: Daily 09:30 -17:00

Opening Times Computer Museum: Colossus and Tunny Galleries Daily 09:30 -17:00

Opening Times Computer Museum: Full Museum - Thursday, Saturday, Sunday 12:00 -17:00

Tickets : Adults £17.25;   Concessions £15.25;   Children (12 - 17) £10.25

Tickets Computer Museum: Adults £7.50;   Concessions £5.00;   Children (5 - 16) £5.00

Tickets Colossus/Tunny: Adults £3.00;   Concessions £2.00;   Children (5 - 16) £2.00

Tel. : 01908 640404