Whatever happened to Block D at Bletchley Park? We go inside the codebreaking building

Bletchley Park has started a new round of fund-raising that will try to raise between £10-15 million to save the infamous Block D at the historic site near Milton Keynes.

Block-D is one of the most important buildings on the Bletchley Park site. The warren-like building was erected in 1942-3 to accommodate the expanding Huts 3, 6 and 8, which worked closely together to break, decipher and analyse German Enigma traffic.

The 10-year plan is to turn the decrepit, dilapidated, and crumbling building back to its former glory for future generations to enjoy and learn about the work carried out in secret throughout the Second World War.

When finished, Block D will let visitors see what went on at the secret location, that wasn't even acknowledged to have existed until the 60s, and how, with the help of over thousand people and some of the brightest minds in the country, German communication lines were cracked.

We've seen first hand that it's restoration work much needed, after Pocket-lint was invited in to see inside the restricted access building.

The building, while solid in its foundations - it was build to look like a hospital to avoid air raids - is badly in need of some love and care. Computers from another era have been left in the foyer, like it's some sort of tech graveyard. Pigeons have taken over; paint isn't just starting to crumble off the walls, but falling off, and the lighting system, the first use of florescent lighting in the UK, is shot.

The building houses some of the most intact and evocative interiors at Bletchley Park. Many of the fittings are still the original ones installed in 1942, including radiators, hatches, coat hooks and Bakelite light switches. In some rooms, it's as if the codebreakers have just left.

In its prime, Block D held a thousand people working around the clock to crack the thousands of encrypted messages being sent by the German forces and internal agencies in a bid to win the war. A pneumatic tube system and conveyor belt sped up communication, while the building itself was built for secrecy, both inside and out.

Its layout, with spurs off a single corridor, was designed to keep different departments separate, so that staff knew only what they needed to. Many of its staff, we are told, thought it was like a tunnel system, and being there in person, it certainly felt like that.

While Block D is part of Bletchley Park's future plans, more imminent plans are about to get started. The historic site has just been awarded £7.4m from the Heritage Lottery Funded restoration programme that will see the derelict Codebreaking Huts, which were made of wood, restored to their 1940s condition and opened to the public.

In April 2013 the physical work started that will restore the Park back to the 1940s, so visitors will be able to experience what the 10,000 people who worked there experienced.

That, according to the Park, means the removal of 21st Century paraphernalia such as car parks, lighting and yellow lines on the road, renovating Block C, and restoring Huts 3 and 6.

Hut 6 is where the Enigma work began before moving to Block D. It's in a worse state than Block D, although caught in the same time bubble. It too hasn't been touched since the codebreakers left. The floors might have started to collapse, but once inside you are immediately transported back to what it would have been like 70 years ago solving messages over 3 shifts hours long.

You can learn more about Bletchley Park and its efforts into shortening the war (some say by 2 years) at the official website - www.bletchleypark.co.uk.