Bletchley Park, the setting of their groundbreaking and lifesaving work of World War II, was scheduled for demolition.

But the stories they had to tell convinced the Bletchley Archaelogical and Historical Society that the site could not simply be turned into a housing estate - and plans were drawn up to preserve it for the nation's heritage.

Alan Turing created the first programmable computer at Bletchley

It has now been reported that the Bletchley Park Trust is on the brink of closing a deal to buy the majority of the 55-acre site near Milton Keynes from its present owners.

The trust is being understandably coy over what it terms as a "sensitive stage" in the proposed transaction, but it promises an announcement next week.

Up until the mid 1970s, the wartime role of the Buckinghamshire mansion and its grounds were known only to a relatively small group of people.

Then, as previously secret papers were declassified under the 30 year rule, the story of the world's first computer complex became known.

Before the Second World War, the site of Bletchley Park had been home to a city financier who bought two farms and acres of land to create a country estate for his family.

Chess players and crossword experts were recruited to the operation

Early in 1938 a local builder bought the site, with the intention of demolishing the house and outbuildings before selling the estate as a housing site. Demolition stopped when the land was bought on behalf of the government.

As it became clear that Britain was heading into another conflict with Germany, the Government Code and Cypher School was moved from the Foreign Office in Whitehall to the site, so that its work could continue away from air attacks.

The first GC&CS staff arrived at Bletchley Park in August 1939, based initially in the mansion.

After a couple of months, the first of a number of wooden huts were built to house the increasing numbers of staff posted out to the facility.

Colossus finally cracked the Nazi cypher

Chess masters, mathematicians, academics, crossword experts and linguists were drafted in to what was affectionately known to those who lived there as the Golf, Cheese and Chess Society.

They were recruited mainly from Cambridge University and included the founder of modern computing, Alan Turing, as well as the likes of Ian Fleming, who went on to write the James Bond novels.

Their main achievements were in cracking the German Enigma machine, which generated a constantly changing code for transmitting radio messages.

Turing's work on the "bombe" - an electro-mechanical machine that greatly reduced the time required to break the daily Enigma keys, led to development of the first computer.

His creation of Colossus - the world's first programmable computer - resulted in the code being broken, giving the Allies the edge they desperately needed.

Intelligence gathered at Bletchley was used in the planning of D-Day

In May and June of 1940, information obtained from a Luftwaffe cypher key helped with the recovery of British solidiers from the beaches of Dunkirk.

Further information helped to plan the RAF fighter defence during the Battle of Britain. The majority of intelligence gathering for D-Day was also carried at Bletchley.

By 1944 the site's intelligence network spanned the globe, with decryption centres in Malta, Cairo, Nairobi, Mombasa, Delhi, Colombo and Brisbane. The radio transmissions of any nation which might have been useful to the allies was intercepted.

Churchill himself said that the work of GC&CS helped to save many lives on Atlantic convoys, and reduced the length of the war by two years.

According to the present-day GCHQ, immediately after WWII intelligence staff abandoned code-breaking to compile a history of the war in the West, based on their daily reports.

A total of 12,000 cryptanalysis staff were then demobbed from Bletchley Park.

In turns, the site was used as a teacher training college, a training centre for GCHQ, a GPO training school and an air traffic control training school. By the time of the 1991 re-union, the site was empty.

Now the future of the site as a permanent monument to the code-breakers who worked there has almost been achieved.

The trust wants to expand the present museum - which attracts 50,000 visitors a year - to an integrated heritage park with the overall theme of "the science of communications".