The Harwell Dekatron, a pioneering computer built from 1949to 1951, has been fired up after 20 years in storage and a three-year restoration project.
The world's oldest original working digital computer will now go on display at The National Museum of Computing at Bletchley Park in Buckinghamshire.
The Harwell Dekatron was first used at the Atomic Energy Research Establishment in Oxfordshire and later in computer lessons at Wolverhampton and Staffordshire Technical College.
It was built to help scientists by performing calculations previously done using adding machines.
The official unveiling on 20 November is to be attended by some of its creators as well as staff that used it and students who learned computer programming on it, according to the BBC.
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Although reliable, the machine took up to 10 seconds to multiply two numbers. It was superseded by smaller computers in 1957.
The Harwell Dekatron then went to the Wolverhampton and Staffordshire Technical College. In 1973 it was donated to Birmingham's Museum of Science and Industry.
After being on show for 24 years, the machine was dismantled and put into storage when the museum closed in 1997.
There it remained until spotted by chance by Kevin Murrell, a trustee of The National Museum of Computing, in a photograph taken by a computer conservationist.
He located the Harwell Dekatron and collect its component parts which were taken to the museum at Bletchley where the restoration took place.
The restoration team was led by conservationist Delwyn Holroyd, who said they had replaced as little as possible so most of the parts on the machine are original.
“The restoration was quite a challenge, requiring work with components like valves, relays and paper tape readers that are rarely seen these days,” he said.
Murrell said: "It's important for us to have a machine like this back in working order as it gives us an understanding of the state of technology in the late 1940s in Britain."