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Bletchley rebooted: The crypto factory time remembered

High commands and dirty words in German – the story retold

You like die 'bang, bang' with the ladies, ja?

It brings me on to the WRENs, who actually ran the code-breaking machines. The WRENs worked in extreme temperatures during summer and winter inside the wooden and then concrete huts, their work was tiring with the shifts running for eight hours around the clock seven days a week.

Bombe operator Ruth Bourne's shift-times were changed each week and that this would screw up people's body clocks. WRENs lost it. Bourne herself went to the Bletchley sick bay one day complaining of feeling “not very well” before collapsing in tears. The doc's prescription: four days sleep with a constant supply of jugs of water by her bed followed by two week’s leave. “Some didn’t recover and go back to work,” Bourne reflects.

The Germans were efficient, but they also made errors. It was their mistakes that gave Bletchley Park's operators crucial breaks in understanding the encryption and messages, as a section called "Cilli" explains. The Germans frequently used the airwaves for dirty talk about their girlfriends, giving the girls a Bletchley plenty of gossip and giggles and allowing the decoders to build up a library of recognisable – if dirty - words. It’s believed Cilli was the name of a German soldier’s girlfriend.

Germany's Italian allies were sloppy, too, typing out full words rather than disguising then - for example, “incrociatore” for cruiser. This caught the Italians out at Cape Matipan in March 1941, the first military victory credited to Bletchley Park. The Royal Navy sank three Italian heavy cruisers, two destroyers and crippled the Italian's flag ship in an action that claimed more than 2,400 Italian sailors for three British lives.

Alan Turing's office in Hut 8, photo: Gavin Clarke

Seat, desk and hard hat of power: Alan Turing's office, Hut 8

But it was the downing of Hitler’s naval pride, the Bismarck, that's the real breath-taker. The sinking of the Bismarck was a priority: a monster ship weighing 50,000 tonnes, it had sunk the Royal Navy's HMS Hood with the loss of 1,416 crew and just three survivors picked up.

The Bismarck was big enough to menace food and supply lines to Britain coming across the North Atlantic from then-neutral North America. Sinking the ship was important not just British morale but also to the armed forces' material chances of staying alive during those dark early days of the war.

Anchored in Norway, Bismarck had slipped out to attack Allied shipping on May 18, 1941. The Naval brass didn’t believe Bletchley’s initial intercept about the ship's movements but when Bletchley decoded a second message between the ship's operators and shore that revealed Bismarck’s final destination as the French port of Brest, the navy scrambled. Three British battleships and 14 aircraft pounded the Bismarck, sinking her on 26 and 27 May, 1941.

The key piece of information that Bletchley decoded? A Luftwaffe officer named Hans Gesserlick on shore had radioed the Bismarck to inquire about the health of a family member among the crew. In this communication the ship's operators told Gesserlick of the Bismarck's destination – Brest.

Bletchley even decoded the last message from the ship's captain - "ship unmanageable, shall fight to last shell, long live the Furher" - and news of the sinking that lunchtime time producing spontaneous cheering in Bletchley’s crowded canteen (the now-disappeared Hut 2).

Rebuilt Bombe Bletchley Park, photo copyrighted

Bletchley's replica of the Turing-designed Bombe, the Park's first code-breaking machine

The guide moves me on. Bletchley is best known for the Tunny and Colossus, introduced because the Germans had upped the intelligence ante with the Lorenz SZ42 cypher machine. Lorenz messages bested the Enigma by using 12 rotors, giving it a possible 1.6 billion billion possible start positions each day. The Lorenz was used for the Hitler and his high command.

The Tunny was designed using simple deduction and inspired genius by Bill Tutte and built by scientists at the forerunner of BT, the General Post Office. Tunny, though, could only process final decrypts. The job of working out the original rotor settings was done by hand and still took days.

Colossus was built to perform numerical analysis of messages and cut the job of working out the start position of those 12 rotors to hours. The secret to Colossus was Thermionic valves – 2,500 by the time of the second Colossus in 1944. Valves were the idea of GPO engineer Tommy Flowers, who'd seen the GPO use the valves in the first, modern digital GPO phone exchanges. Between 15 and 20 Tunnys and 10 Colossi worked at Bletchley.

Colossus played a major role in the success of the Allied landings in June 1944 - the landings that paved the way to eventual victory. The Allies had been distributing false intelligence that the landings were to take place in Calais. Listening to the messages from the ambassadors of German ally Japan on troop movements and on defence plans for Northern France, Bletchley learned the German High Command had swallowed the Allied deception. With the bulk of Hilter’s defensive forces concentrated in Calais, the Allies landed 233 miles (375km) south in Normandy.

They did what around the lake?

The guide tells about Tunny and Colossus on a trip around the lake at Bletchley Park. This is a bit confusing but is explained because the machines ran in the buildings that now comprise The National Museum of Computing History (TNMOC), a few seconds’ walk from the Bletchley manor and huts. Also, they were in a hut pulled down years ago with its site now beneath a car park. You can see the rebuilt Tunny and Colossus at TNMOC.

The guide is winding up and I’ve ground to a halt by the lake.

Time for refreshments. There’s a decent Bletchley Park café, called Hut 4, tucked in next to the manor house. Hut 4 has adopted the National Trust template for refreshing the general public: spacious and well-presented, it serves hot meals, lush cakes and muffins, delicious soups – I opt for the carrot and coriander – and ready-made sandwiches. There’s not much food-wise around Bletchley, so Hut 4 than takes up the slack.

The self-guided tour takes about an hour and a half. You can either combine it with a visit to TNMOC – where you'll see those Colossus and Tunny rebuilds – or rejoin the world back in Milton Keynes (the next train stop north) and head back to London Euston in less than an hour. You could also pop over to Oxford and Cambridge, where many of the brains for Bletchley including Turing were recruited at the start of the war.

If you want to stay in the area, there’s plenty of places to stay, visit and shop at in Milton Keynes and cities of Oxford and Cambridge. If you want to stay local, though, there’s the Bletchley Park B&B.

Bletchley has a challenge. Fans of British tech will likely feel they know about the Bletchley story. Everybody else will overlook Bletchley's role in WWII thanks to the legacy of the Official Secrets Act and that dominant narrative.

But the self-guided tour changes this. It sheds new light on familiar chapters in the war and the surprising role Bletchley Park played. Moreover, the guide helps put names and faces to the people behind the more familiar Turing and behind the mighty Colossi – people without whom Bletchley couldn't have functioned as it did.

My advice: go to Bletchley and plug in. ®





Getting there

By train: between 30-50 minutes from London Euston to Bletchley. By car: between the A5 and A421, north of London.


Winter opening: 1 November to 28 February, 9.30am to 4.00pm.
Summer opening: 1 March to 31 October, 9.30am to 5.00pm.
Entrance fee: adults £15, children 12-16 £9, under-12s go free, family tickets £34.
Concessions available.

Visitors to Bletchley Park can visit the Tunny and Colossus at TNMOC. Charges are £2 for the Tunny and Colossus galleries and £5 for the whole museum. The TNMOC Colossus and Tunny galleries are open daily; the rest of TNMOC is open every Thursday, Saturday and Sunday afternoon from 1pm.

Bletchley Park website

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