Bletchley Park's wartime code breaking huts in disrepair
20 March 2013 Last updated at 00:29 GMT
During World War II, Bletchley Park was the top secret home for Britain's code breakers.
But that secrecy, which lasted for decades after the war, came with a price - many of the buildings where vital work took place were left to ruin.
The plan now is to restore them.
Before work began, Bletchley's chief executive Iain Standen gave security correspondent Gordon Corera a tour of one of the huts.