Originally built in 1951, the Harwell Dekatron or "Witch, said to be the world's oldest computer. It has been rebooted at the National Museum of Computing at Bletchley Park in the U.K.

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Restored 61-year-old Harwell Dekatron. The computer was built and used at the Atomic Energy Research Establishment in Harwell, Oxfordshire, from components more commonly found in a British Telephone exchange.

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Weighs 2.5 tonnes. Once voted the world's most durable computer. WITCH has 828 flashing Dekatron valves, 480 relays and a bank of paper tape readers.
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WITCH team Peter Burden, Bart Fossey, Kevin Murrell, Dick Barnes and Ted Cooke-Yarbrough.