Harwell Dekatron / WITCH History

The story behind the Harwell Dekatron / WITCH computer is an enthralling one. It has led a charmed life and on three occasions has been brought back from the brink of destruction.

You can read the full history of the Harwell Dekatron in a new book by Kevin Murrell and Delwyn Holroyd. Meanwhile here is the potted version:

Design of the computer began in 1949 at Harwell where there was a pressing need to automate the calculations then being performed on hand calculators by human "computors" (as they were then known). Construction was completed in 1952 when it was passed to the mathematicians to exploit its reliability -- when required it ran for more than 90 hours a week in its first year, although its speed of performance was that of a tortoise rather than a hare.

By 1957 it was becoming obsolete at Harwell and was offered in a competition to an educational establishment proposing its most appropriate use. It was won by the Wolverhampton and Staffordshire College of Technology who used it as the Wolverhampton Instrument for the Teaching of Computation from Harwell (hence its later name, the WITCH).

In 1973, it was recognised by the Guinness Book of Records as "the world's most durable computer" and was again retired, this time to the Birmingham Museum of Science and Industry. When that Museum closed in 1997, it was put into storage, but was rediscovered by TNMOC in 2009 and a successful proposal was made to move it to TNMOC for restoration.

Restoration was completed in November 2012 and the best way to display this example of early scientific computing is now being planned. In 2013, it was again recognised by Guinness World records, this time as the world's oldest original working digital compute.