By Thelma Etim
BBC News in Bletchley Park
It has taken 10 years and about 60 volunteers to rebuild piece-by-piece a replica of the Turing Bombe - the vital machine which cracked the Nazis' Enigma Code.
Against seemingly impossible odds the electro-mechanical device enabled cryptographers to decode more than 3,000 German messages in a day, changing the course of World War II.
The Turing Bombes were once Britain's best kept secret, but on Wednesday members of the project team - among them retired computer experts and telecommunications engineers - demonstrated how codes were broken at Bletchley Park in Milton Keynes.
John Harper, the 69-year-old former chartered engineer who oversaw the team of enthusiasts, never doubted the ambitious plan would come to fruition, but he said: "It has been difficult and I am totally shattered.
"The first two years were a re-drawing exercise, we did not actually start making the machine.
'Passion and drive'
"We had draftsmen using computing techniques. If we started making parts and we were not sure of what we were doing it would have been a wasted effort.
"But I always felt it was achievable. The team's passion and drive even outstripped me."
The majority of the work was carried out away from Bletchley Park, once at the heart of the world's biggest secret communications network.
Some of the team members worked at home in the evenings, others even had their own workshops. They met once every 10 days to assemble, fit and check the parts were ready.
The father-of-three added:"It was something worthwhile, a tribute to those that worked on it during the war and did not get the recognition because of the secrecy aspect - unfortunately, some have passed on."
Ruth Bourne only told her husband about her wartime job in the 1970s
The device was invented by the mathematical geniuses Alan Turing and Gordon Welchman.
Winston Churchill famously described the code breakers as "the geese that laid the golden eggs but never cackled".
Widow Ruth Bourne, 80, had to wait until the 1970s before she could reveal to her husband Stephen Bentall what she had been up to during the war.
Bound by the Official Secrets Act, Ms Bourne, who was an 18-year-old Wren at the time, could not even tell her mother.
She explained: "I was keen to do my bit, a lot of my relatives were in the Holocaust and I wanted to see the Germans defeated.
"I volunteered for the Wrens three times - the first time was at 16, but they turned me down.
"After the swearing in, we were told the pay would be poor, there would be little prospect of promotion, we would work anti-social hours and once you accepted you could not leave."
Wren 78519 - as she was known then - was taken to another room to sign the Official Secrets Act, and then to another, where she was told she would be breaking the German code.
Bletchley Park's employees worked on a "need to know" basis
"It was all hush, hush," she said. "My mother said: 'You can tell me - I am your mother after all.'
"Had I known then what I know now I would have found it very difficult to keep a secret. At 18 you are not mature.
"There were between 10 and 12 machines in bays, it was very noisy and very boring. It was not an easy job and you had to concentrate but you were very satisfied when you cracked a code."
Ms Bourne was one of a number of Wrens who dismantled the devices "wire-by-wire" at the end of the war.
"It was only when I saw the Enigma machine at a lecture at the Royal Geographical Society about 15 years ago, that I realised the enormity of what I had been involved in during the war," she said.