Saturday, 19 June 2021

Wargrave local history club

ON July 14, we visited Bletchley Park, home of the wartime codebreaking team.

ON July 14, we visited Bletchley Park, home of the wartime codebreaking team.

The large site has benefited from Heritage Lottery funding, enabling the restoration of several of the surviving buildings, which are themselves of historic interest.

The buildings also house displays about the work done at Bletchley Park.

The site was developed with a large mansion in the 1870s and the house, together with the estate, was bought in 1883 by Sir Herbert Leon. It remained a family home until it was put up for auction in 1937. The Government acquired a large part of the estate, including the mansion, in 1938 and soon built the first of many wooden huts there.

These housed the government code and cypher school. Bletchley Park’s rural location meant it was less at risk from wartime attack and it had easy access from Oxford and Cambridge as well as London.

The displays and exhibits show the challenges the codebreakers faced. There are examples of the machines used by the German forces to code their secret messages.

Although known as Enigma machines, there were several variants, used by the army, naval or air forces, and also the German secret service.

The “simplest” of these had three rotors which encrypted the message being sent. The rotors could be set to any one of 159 million, million million combinations (and the particular set-up was usually changed daily) and was different for each of the services that used the Enigma machines.

The machine advanced the rotor positions as each character was typed, so if the letter E was encrypted as Q the first time it occurred in a message, it would be something different the next time it occurred.

The idea for such machines was not new — they had been invented in Holland in 1915 for the secure transmission of information by banks. Machines had been bought by Britain, so the way they worked was known.

The problem was to work out what the particular day’s settings were for each of the four services.

The codebreakers used a combination of the technology of the time as well as brainpower and intuition to solve what at first seemed an impossible puzzle.

There were some standard phrases that were likely to occur in a message and as the Germans did not use numerals, the word “eine” was likely to occur quite frequently. If such patterns could be discovered, the day’s code could be unlocked.

To be effective, the messages had to be decoded (and then translated, of course) quickly.

The way forward was a machine known as a “bombe”, developed by Alan Turing and Gordon Welchman.

This was, in effect, a motor-driven set of Enigma type wheels that could run through all the possible combinations and would stop if a possible match was found. It might also stop if there was a machine fault, so the results needed further interpretation.

The displays at Bletchley Park also give the biographies of some of those who worked there and describe the social life of those who worked on decoding the messages as well as the methods of getting messages back to be decoded, be it by pigeon or motorcycle dispatch rider.

The society will resume its programme after the summer break on September 8 with a talk on the geology of Bowsey Hill.

On October 13, Roy Sheppard will recount the history of postcard collecting and on November 10 author Anthony Poulton-Smith will explain the origins and meanings of Berkshire’s place names and how they have changed.

Meetings take place in the pavilion in the recreation ground at 8pm.

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