World’s Oldest Computer To Be Restored At Bletchley Park


The restorers claim the challenge is the computing equivalent of raising Henry VIII’s Tudor flagship the Mary Rose

A computer which is being called the oldest “original functioning electronic stored program” machine of its kind is being restored by a group of volunteers at the former World War II code-breaking centre at Bletchley Park.

In a statement released this week, the group restoring the Harwell computer, later known as the WITCH computer, from the National Museum of Computing (TNMOC) at Bletchley said that when the machine is restored it will be housed alongside Colossus Mk II which is said to be the world’s first electronic computer.

To help fund the restoration, and extend the museum, the TMOC team are asking for members of the public and industry to sponsor the work by buying one of 25 shares at £4500 each. Sponsors on board already include IT integrator Insight Software.

The Harwell computer earned its WITCH nickname in the long-respected tradition of contrived IT acronyms: it was used by Wolverhampton University – hence Wolverhampton Instrument for Teaching Computing from Harwell (WITCH).

“The machine was a relay-based computer using 900 Dekatron gas-filled tubes that could each hold a single digit in memory – similar to RAM in a modern computer – and paper tape for both input and program storage,” said Kevin Murrell, a director and trustee of TNMOC.

Murrell added that while the machine could never be classed as speedy – the WITCH was build for reliability. “It was definitely the tortoise in the tortoise and the hare fable. In a race with a human mathematician using a mechanical calculator, the human kept pace for 30 minutes, but then had to retire exhausted as the machine carried on remorselessly. The machine once ran for ten days unattended over a Christmas/New Year holiday period.”

The Harwell computer is due to arrive at the TNMOC on Thursday 3 September with the restoration expected to take up to a year. “The TNMOC team of engineers are eager to start the restoration work,” said Murrell. “ It’s the computing equivalent of the raising of the Mary Rose and they are up to challenge!”

The National Museum of Computing at Bletchley Park is an independent charity and houses the largest collection of functional historic computers in Europe.

Earlier this week Scientists and academics including Sir Richard Dawkins announced they were backing an online petition calling on the government to publicly apologise for the treatment of computing pioneer Alan Turing – based at Bletchley during the war – who committed suicide in 1954 after being prosecuted and vilified for his sexuality. The petition has already attracted 25,000 signatures and can be reached at

In May, the UK government rejected requests that Bletchley should be elevated to the same status as the Imperial War Museum. The government said it was keen to support the site but there would be no moves to link the site to the Imperial War Museum.


(WITCH: image from TNMOC)

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