TWO of the original designers of the world’s oldest digital computer rolled back the years as their creation was re-booted for a new generation.

Dick Barnes, 92, and Ted Cooke-Yarborough, 93, looked on proudly as the Harwell Dekatron whirred back into life after being painstakingly reconstructed by volunteers and experts at The National Museum of Computing (TNMOC) at Bletchley Park, near Milton Keynes.

The duo were part of a small, pioneering team at Harwell Atomic Energy Research Establishment who created the 2.5 tonne machine, the size of a small room, in 1951.

Mr Barnes, from Abingdon, said: “It came about after a chance remark about the need for computing power and it provided a number crunching facility for physicists.

“The art of programming required was so basic but you can actually see what the computer is doing whereas young people today have no idea how a computer works.”

Mr Barnes revealed the Dekatron has less computing power than an average modern calculator and less processing ability than a digital camera. He added: “I think modern computers are marvellous and the advances have been fantastic when you think that a smartphone has a much more powerful processor than this room full of equipment.”

The Dekatron could not be more different from the Emerald super computer which was launched by Harwell scientists earlier this year.

The million-pound machine will be used by researchers to crunch medical research data for vaccines, create software for the world’s most powerful radio telescope and see how human action is likely to affect the climate.

Experts at the museum believe the Dekatron is the oldest computer in the world still to be using its original parts which were built using components designed for TV and radio sets.

Mr Cooke-Yarborough from Longworth, near Abingdon, said: “Our job was to use electronics to help our research programme. Most of the calculations up to that point had been done by people using mechanical calculators which was terribly tedious work.”

The computer was used at Harwell for six years before being taken to the Wolverhampton and Staffordshire Technical College where it was renamed the WITCH (Wolverhampton Instrument for Teaching Computation from Harwell).

In 1973 it was moved to the Birmingham Museum of Science and Industry before being put into store. Then, in 2008, it was discovered by museum staff and the restoration project began.


The Harwell Dekatron:

  • Size: Two metres high and six metres deep (a small room)
  • Weight: 2.5 tonnes
  • Features: 828 flashing Dekatron valves, 480 relays and a bank of program tape
  • Power consumption: 1.5kW

Apple iPad mini: 

  • Height: 200mm and 7.2mm deep
  • Weight: 308 grammes
  • Features: FaceTime HD camera, iSight camera with 1080p HD video recording, ultrafast wireless, access to more than 275,000 apps
  • Power consumption: Lasts 10 hours on a fully charged battery


  • 1949: Design begun
  • 1957: Sent to Wolverhampton
  • 1973: Moved to Birmingham Museum of Science and Industry
  • 1997: Storage at Birmingham Collections Centre
  • 2009: Moved to The National Museum of Computing
  • 2012: Rebooted to become the world’s oldest original working digital computer