The Harwell Dekatron, more commonly known as the WITCH, was built in 1951 to replace staff at the Harwell Atomic Energy Research Centre. Designed to crunch numbers, the 2-and-a-half tonne machine contains 10,000 moving parts and takes up to 10 seconds to multiply two numbers. Though no faster than a pocket calculator, it could work non-stop for up to 80 hours a week and was famed for its reliability.
In fact, talented human mathematician EB ‘Bart’ Fossey once pitted his calculation speed against the Harwell Dekatron. While he could initially keep pace he had to give up after about half an hour due to exhaustion while the machine kept ticking away.
However by the end of the decade, the Harwell Dekatron was finding itself outpaced by newer, faster computers. It was moved to Wolverhampton and Staffordshire Technical College (now Wolverhampton University) where it was used for teaching purposes. It was here that it earned the nickname WITCH, which stands for the Wolverhampton Instrument for Teaching Computing from Harwell. In 1973 WITCH was moved to the Birmingham Museum of Science and Industry, where it remained on display for 24 years, until the museum closed in 1997.
WITCH remained disused in storage for over a decade until, by chance, Kevin Murrell, a trustee of the National Museum of Computing spotted part of it in a colleague’s photo. With help from the museum’s staff he then began a three-year-long mission to track down the machine’s missing parts and restore it to working order.
The historic computer is now on display at The National Museum of Computing in Buckinghamshire.