Some of Alan Turing's notes have been found blocking holes in the roof at Bletchley Park

Alan Turing's top secret documents that helped work out what the Nazis were up to during World War II would probably be the last thing you'd expect to find in the walls of an old hut. But that's exactly what the team at the former codebreaking fortress Bletchley Park discovered while restoring the site.

First reported in The Times, the revelation came during multi-million pound restoration work at the property in Milton Keynes, Buckinghamshire. Bletchley Park is now a huge heritage attraction, more so since the film based on the life of the pioneering computer scientist, The Imitation Game, came out.

Now, projects and showcases are unearthing amazing new material which helps to further highlight the work of Turing and his colleagues. Between 1939 and 1945, more than 10,000 people were based at the UK Government Code and Cypher School HQ.

The papers were used to break the Nazi's enigma code, and were found inside Hut 6, where Turing worked, Bletchley Park Trust told Business Insider UK. The charity, which runs the site, said the documents were found in the roof of the building, screwed up and stuffed into holes to stop draughts coming in through the roof.

Some of them are the only surviving examples of "Banbury sheets", The Times explains, which is a method created by Turing to help decipher Nazi messages more quickly. The fact they were stuffed inside wall cavities breaks security rules too, given that workings-out were supposed to be destroyed after use.

Bletchley Park's Director of Learning and Collections, Victoria Worpole, said in a statement:

It's quite rare for us to find new paperwork because any that survived is in either our archive, at GCHQ or the National Archive so to find actual materials that were used by the Codebreakers, shoved between beams and cracks in the woodwork is really exciting. We've had a conservator work on the materials to make sure we preserve them as best we can. It's quite interesting to think that these were actual handwritten pieces of codebreaking, workings out. There are some pieces of paperwork that we can't identify. Nobody seems to be able to work out what they are - we've sent things off to GCHQ - and there are a number of items that we've yet to understand properly. We're unveiling a mystery.

The documents form part of a new exhibition called "The Restoration of Historic Bletchley Park." Bletchley Park Trust said that it will reveal "archaeology and codebreaking materials found stuffed into the eaves and the cracks in the huts," revealing how workers deciphered Nazi secrets.

The trust mentions that more material was found:

Amongst the fragmented codebreaking documents located in the roof of Hut 6 were also parts of an Atlas, a pinboard and a fashion article from a magazine. These will be displayed alongside other items that were discovered during the restoration project and these include a fragment of 1940s teapot, glass bottles including one for Chicory, archaeological items such as bricks from Block F (demolished in 1987) and a 'time capsule' left inside a door in Hut 11A.

The documents were actually uncovered in 2013 but have only just been released. At the time, they were frozen to prevent further damage, then cleaned and repaired.

Chief executive of Bletchley Park, Iain Stander, spoke to a local newspaper about the artifacts:

Discovering these pieces of code-breaking ephemera is incredibly exciting and provides yet more insight into how the codebreakers worked. The fact that these papers were used to block draughty holes in the primitive hut walls reminds us of the rudimentary conditions under which these extraordinary people were working. These are the actual documents used by codebreakers, and in terms of the codebreaking process they are pivotal," added Gillian Mason, Bletchley Park curator. "I can just see these people beavering away. There is a lot of pencil and crayon activity.