The Harwell Computer - a conservation project

One of the oldest surviving computers, designed in the UK between 1949 and 1951. Restoration was completed in 2012, supported by the Computer Conservation Society.

  • Designed to carry out complex repeated calculations.
  • A digital machine with 90 8-digit registers for internal storage (using Dekatron valves). Operated as a stored-program computer, with a multiplication time of between 5 and 10 seconds.
  • The computer was used in the design of the UK’s first nuclear reactors at Harwell, until it was retired in 1958.
  • Then used in education at Wolverhampton for teaching students until the 1970s (and renamed WITCH).

Restoring the Harwell Computer

  • Restoration started when the machine was moved from storage to Bletchley in 2009 - watch a BBC video of the move.
  • The machine was rebooted in November 2012 - watch a video of the event
  • Now recognised in the Guiness Book of World Records as the world's oldest working digital computer.
  • You can see the restored machine at The National Museum of Computing at Bletchley (TNMOC) - check the TNMOC visiting times

For more about the Harwell Computer

  • There is a good amount of original documentation about the computer and its use available online - along with many photos - see the CCS project pages, there is also a good Wikipedia entry.
  • These resources provide material for further study and historical investigation.
  • This restoration project is one of a number of active Computer Restoration Projects being carried out by volunteer members of the CCS. You can find more about the CCS on this website, and meet people involved by coming to one of our CCS events, or visiting the machine at TNMOC in Bletchley.

Photos courtesy of The National Museum of Computing.