Alan Turing paused to peer at the sign saying `Bernard Lovell - Director - Jodrell Bank Experimental Station' before knocking on the door of the rather undistinguished building.

"Come on in!" shouted Lovell. "What do you think about this new telescope we're building? It'll be the largest steerable radio telescope in the world! All that naval surplus from the war will serve very well. It's very exciting!"

"I'm sure it is, but you can tell me about it another time. I've a favour to ask you. Do you recall my Universal Machine?" asked Alan.

Lovell shook his head. "It's a theoretical device," Alan went on. "It explains the limits of what a computer can and cannot do. If a Universal Turing Machine can perform a task in theory, then a real computer can be programmed to actually complete that task in practice."

"But it's still a theoretical device, you can't actually build one, can you?" asked Lovell; "unlike a radio telescope", he muttered under his breath.

"No," replied Alan. "But, building the Bombes to decipher the Enigma machine and my more recent involvement in "The Baby" computer got me thinking. I think I've designed a device that can be built and should be able to crack any code, no matter how complicated."

"Hmm," said Lovell thoughtfully. "The Government would surely fund you to build such a device."

Alan looked down, sadly. "That's the problem. The police are investigating my private life. There's a court case coming up, and I'm being watched by the secret service. I can't build this device at the moment. The powers-that-be don't trust me. But you, you've got so many electrical spare parts here for your telescope that I'm sure your engineers could build it. Would you do that and then hide the device away somewhere until this unpleasantness in the courts is over?"

"Of course. I think I know just where to hide it," said Lovell, and the two men watched as the workmen prepared to break ground for the telescope's foundations.

--

"Will you please welcome to the stage, ... Mike and Ellie!"

As the rest of the children clapped, a somewhat embarrassed Mike and Ellie shook the headmaster's hand. "Thanks to you two," praised Mr Thornhill, "the Egyptian Enigma was solved and the Manchester Museum now has a spectacular new exhibit; and the School has had plenty of good publicity!"

"Well, it wasn't just us," explained Mike. "We had a lot of help from Mr Barquith - although we always called him Mr B. Nowadays he works at the Manchester Museum, but a long time ago Barquith was one of Alan Turing's students."

"Yes, we wouldn't have been able to solve the Egyptian Enigma if it hadn't have been for Barquith!" carried on Ellie.

"Well," said Mr Thornhill, "it turns out that we've been sent a code-breaking challenge by MI5 themselves! They've organised a cryptography competition for schools to find the next generation of code-breakers. Let's see if you're smart enough to crack this!" As Mr Thornhill spoke, a picture appeared on the screen behind him.

As they returned to their seats, Ellie whispered to Mike "I think I see what to do. I'm sure we can crack it after school."

Later that afternoon, as the bell went, Mike and Ellie raced off straight past a car with blacked-out windows. "Good-o," said the car's occupant, "they appear to have taken the bait".

Alan Turing Cryptography Competition 2014 is organised by the The Department of Mathematics at The University of Manchester.
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