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Bletchley Park

Last week I had the great opportunity to visit Bletchley Park and learn about some of the history some of which may not be as widely known as Alan Turing and the use of Colossus at Bletchley Park during the war.

The admission cost is £15 & £13 concessions& however it does entitle you to a year's entry to the estate, which I found fair as it is quite extensive and I'm unsure you could fully view it in one visit; there are also 2 for 1 entry offers if arriving by train.

Bletchley Park is considered the home of British WWII code-breaking and is where the forerunner of modern computing, Colossus was conceived and developed by the slightly less well known Post Office Electronics Engineer Tommy Flowers. Sadly the original Colossus is no longer in existence as it was dismantled at the end of the Second World War, presumably to maintain its secrecy. However some remnants of the machine which helped enable you to read the very post do remain within the museum at Bletchley Park.

But Bletchley Park is far more than just the birthplace of Colossus. It is such an ordinary place for such extraordinary actions to have taken place, it is an incredibly beautiful estate which seems so serene and could still be a country house whose gates have been opened; it is difficult to imagine 10,000 people rushing in and out each day from their lodgings, as they carried out their 8 hour shifts 24/7.

A little history of 'Bletchley Park'

Originally part of the Manor of Eaton, The estate was first referred to as 'Bletchley Park' during the ownership of Samuel Lipscomb Seckham, who acquired it in 1877. The estate was sold in 1883 to Sir Herbert Samuel Leon, a Liberal MP who expanded the existing farmhouse into the present mansion.

In July 1938 Admiral Sir Hugh Sinclair, the then Director of Naval Intelligence and head of MI6 purchased the land and mansion with his own private funds, the amount paid for the 55 acre estate and mansion was £6,000; an amount equivalent today to £282,357. This was done as he had failed to convince the government of the need for and indeed to underwrite, a new headquarters removed from the capital as successor to 'Room 40' - the code breaking HQ of the First World War. To maintain secrecy, the reason used for the activities at Bletchley Park between August and October of 1938 a fictitious 'Captain Ridley's Shooting Party' was created, the real reason for their presence was to determine the feasibility of Bletchley Park as a remote operations centre during wartime.

Bletchley Park was chosen as a location due to three key features it possessed:-

  • The privacy of being set in its own estate
  • The transport links located next to the estate with close links to both Oxford and Cambridge, of which many of the code breakers were alumni.
  • An isolated power and water supply - ensuring further secrecy with activities and a secure source of drinking water

During operations, it became evident that the mansion would not be significant for all operations, thus 'huts' were built to accommodate the individual sections these included:

Hut 1 The first built in 1939 initially housed the first Bombe, "Victory"
Hut 5 German police codes & Military intelligence (including Italian, Portuguese & Spanish ciphers)
Hut 7 Cryptanalysis of Japanese naval codes and intelligence
Hut 11 Bombe building

And the paired huts of 3 & 6 and 4 & 8 where one would receive the communication then decrypt it and the other would scrutinise the content for military use.
Hut 3 Intelligence: translation and analysis of Army and Air Force decrypts
Hut 6 Cryptanalysis of Army and Air Force Enigma

Hut 4 Naval intelligence: analysis of Naval Enigma and Hagelin decrypts
Hut 8 Cryptanalysis of Naval Enigma

These huts were then developed into Blocks as the war progressed.

Block A housed Naval Intelligence.
Block B contained Italian Air and Naval, and Japanese code breaking.
Block C was devoted to the storage of the extensive punch-card index.
Block D became the home of the Enigma work, extending to huts 3, 6, and 8.
Block E devoted to the incoming/outgoing Radio Transmissions & TypeX machines.
Block F accommodated the Newmanry, Testery and Japanese Military Air Section
Block G housed Traffic analysis and deception operations.
Block H was home to the Lorenz operations and Colossus (now The National Museum of Computing).

Bletchley Park was actually bombed during the war; however it appears it was wholly by accident due to its excellent transport links, which were the intended target. A German bomber returning to base appears to have emptied it payload on what it saw as an opportune target, although missing the main house, the bombs did cause one Hut, housing Naval Intelligence to move 3 feet on its foundations from the shockwave, the workers inside continued to decrypt their messages, whilst others hauled the hut back into place.


To enable the decryption of the enigma machines, the cryptologists had to first ensure they were using the correct settings, this might seem simple but given that the number of permutations of the rotors increased in 1938 from 6 (1 x 2 x 3 = 6) to 60 (5 x 4 x 3 = 60) when the 4th and 5th rotors were added to the rotation, and there being 158 Million Million Million possible ways a standard army Enigma machine pinboard could be set up, they needed to devise a far more effective way to decipher the settings, as they only remained current for 24 hours and any time spent deciphering the settings meant less time deciphering the messages.

Bombe Internal

There was the possibility of capturing the monthly key sheets but the Axis had developed some ingenious methods of devaluing their worth to allied forces, these included printing the month in reverse chronological order so as each day passed it was destroyed making it less valuable and for navy enigma machines, printing the key sheet on paper which dissolved in seawater.

The result of this was the improvement of the Polish 'Bomba' (constructed to emulate 6 enigma machines) into the British 'Bombe' which contained 36 drums, these machines replaced upto 100 workers enabling them to complete other tasks. The 'Bombe' worked not by determining the correct settings but by eliminating the incorrect settings leaving the most likely option, doing this in a matter of 30 minutes.

Alan Turing had designed the initial idea to increase to 36 enigma-equivalents in 1939 to combat the additional 2 rotors but, it was Gordon Welchman who refined it into a physically workable method by eliminating the unworkably long cribs required in Turing's theory to sufficiently rule out large amount of settings. Welchman's improvement was though the use of an attachment called a diagonal board which further improved efficiency.


Although thought of as a German machine used within Word War Two, the Enigma machine was first invented by Two Dutch naval officers R.P.C. Sprengler and Theo A van Hendel, in January 1915 as a way to encrypt messages. The German connection came later in 1918 when German businessman Arthur Scherbius purchased and patented the idea. It was also far more widely used than just by German military, By 1926 Scherbius had sold the idea to German banks, businesses, the post office and anyone who required a more secured method of communication to replace wireless telegraphy or 'Morse code'. Within World War Two an estimated 50,000-100,000 machines were built and used by the Axis powers of Germany, Italy and Japan.

The enigma machine itself was actually first solved prior to World War Two, in 1932 by Polish mathematician and cryptologist Marian Adam Rejewski and his colleague's Jerzy Rózycki and Henryk Zygalski who solved the plug board-equipped Enigma machine.

Enigma Machine

Their success greatly aided the work to be done at Bletchley Park rumoured to have given the code breakers a 2 year head start on the decryptions, they handed their findings to French and British intelligence representatives, merely five weeks before the German invasion of Poland in 1939 and cited the deteriorating political situation within Poland and not technical difficulties for their actions. After the fall of Poland 1939 and then the fall of France many Polish code breakers came to Bletchley Park to aide in the effort, they were however not widely welcomed nor afforded the same clearances as their British counterparts.


The first time an enigma message was deciphered in January 1940 by a team led by Dillwyn 'Dilly' Knox in a small cottage known as 'Bungalow 3', today it serves as the estates management office of Bletchley Park. Within bungalow 3 in 1941, another notable event occurred the decryption by Mavis Lever of a message from the Italian high command to a Mediterranean battle fleet, ordering the attack of an allied troop supply line to Greece. this decryption led to 'The Battle of Mattapan' which enabled the allied forces to make a pre-emptive strike on the unsuspecting ambushing fleet, the forewarning also enabled the allies to create a deception to mask their code breaking ability, sending up a decoy reconnaissance plane.

Bungalow 3(RIGHT)

In addition to breaking these German codes, the codebreakers at Bletchley Park also cracked a 5 pin wheeled Swedish machine called 'C36 Heglin' used in France & by the Italian Navy and paper based cyphers such as a book cypher nicknamed 'Barbara' which utilised double transposition. There was however one machine which managed to stump the codebreakers at Bletchley Park, the SG-41, the final cypher machine developed by Germany during WWII in 1944 and the intended successor to the Enigma, it utilised 5 rotors, identical to late model Enigmas and a paper tape mechanism.


The codename given to the Lorenz encryptions introduced in 1942 was 'Tunny' these were used for high priority orders direct from Berlin in place of the Enigma due to its increased encryption. In 1943, with Colossus decrypting a great quantity of Tunny messages a KGB double agent John Cairncross later of MI6 and rumoured to be the 5th member of the 'Cambridge Five' Spies. smuggled decryptions due to be destroyed out of the Army/Air Force Intelligence base of Hut 3 in his trousers, later transferring them to his bag at Bletchley station before traveling to London and handing them over to his KGB contact.


Colossus is often incorrectly named as the machine used to decrypt the enigma machines; it was however sued to decrypt the Lorenz cypher used by the Germans to transmit radio teleprinter messages which were strips of paper with sequences of removed to convey a message.

Colossus is where modern computers can be traced from. It was the first programmable 'computer' able to study paper tape at 5,000 characters per second with wheels of paper traveling at up to 30 miles per hour. This meant that the incredible volume of calculated work that needed to be done could be carried out within hours, not weeks.

However, typically British whilst what was to become the first modern 'computer' was in construction a few hundred yards away, the cryptographers in nearby huts were utilising a rather less complicated but effective method of communication between themselves a piece of string and a shoebox.


Alan Turing was and is such a famous name in computing, it's quite hard to describe just how much he contributed to modern day technological advances, with the early work on Colossus with Tommy Flowers and to this day the implementation of the 'Turing test' top determine the level of Artificial Intelligence of machines.

Many people may have heard of his name but may not know what befell him. In 1952 Turing was convicted of 'gross indecency' - a term at the time used to define the act of being homosexual, Turing pleaded guilty to this as he felt no remorse for his orientation and was given the option of imprisonment or hormone therapy, he chose the latter which lasted a year and resulted in impotency and gynecomastia, the development of breasts due to the artificial oestrogen within the injections. Due to this conviction his security clearance was revoked and with the exposure of the first two members of the 'Cambridge Five' due to his orientation and fears of homosexual entrapment by spies, he was allegedly placed under additional scrutiny within the 1950s as a potential security leak.

In 1954 Turing was found dead due to cyanide poisoning, which was ruled a suicide. An apple which lay close to him is thought to have been the source. Its speculated that the apple may be a nod to Snow White, one of his favourite stories or through inhalation due to an experiment also found in his home, whatever the true cause, on that day the world lost an incredible thinker and a pioneer of computing.

The people behind Bletchley Park have with the aid of a donation from Google, a National Heritage Memorial Fund and public donations managed to preserve and create such a wonderful memorial to him and his work within their museum; including items ranging from his teddy bear "Porgy", used to practice his speeches on, to a letter written to his mother by a fellow academic some years after Turing's suicide expressing how vital his efforts were to assisting the codebreaking and the war effort.

Significant additions to the exhibit are Stephen Kettle's statue of Turing composed of individual pieces to create a whole, a possible nod to his codebreaking and an original signed apology by the then Prime Minister Gordon Brown acknowledging both Turing's contributions, something which was taken from him with the revocation of his security clearance and the '�appalling way he [Turing] was treated�. In July 2013, the House of Lords proposed a posthumous pardon for Turing's conviction, the same week same sex marriage became legal within the United Kingdom.

Stephen Kettle Turing Statue

Turing Appology

In addition to the exhibit there is a recreation the office of the 'head of hut 8', this was held by Turing and includes details such as a mug padlocked to the radiator, just as it was during his time there due to being issued only one per person.

Alan Turing's office

I thoroughly enjoyed my day at Bletchley Park and it was indeed a full day - lasting 6 hours including a free hour long guided tour of the grounds. I plan to return in mid-2014 to view the exhibits I missed on my first visit and when Block C and the surrounding area is fully restored to its original 1940s style and to undertake the multimedia guided tour. I really would recommend visiting Bletchley Park if you get the opportunity; as it is such a vital part of wartime history and an incredibly interesting place, which still contains still contains quite a few secrets as there are still some wartime activities which remain classified.

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