Of course that is easier said than done, there was only one WITCH ever built. It was 61 years ago that the Wolverhampton Instrument for Teaching Computation from Harwell saw its debut. While today the manufactures aim for compactness, speed, and agility, the WITCH boasted none of the above! It was instead a 2 ½ ton energy hogging colossus that could store just 90 numbers.


OK, so it was not very portable, didn’t run Windows and had the reliability of a British Triumph Sports car with Lucas Electronics. But it was among the first generation of digital computers. It is from the likes of WITCH, ENIAC, and Alan Turing’s work on Bombe and Colossus that that the digital age dawned.

After much effort, WITCH (aka the Harwell Dekatron) has been restored to its former glory. You can read about it here.

I never met the WITCH, but I have a personal affinity to it. The WITCH was decommissioned in 1957, I was two at the time! It was not until 1972 that I heard about the wonderful Dekatron. Harwell at that time was the key research facility in the UK about atomic energy. No, they weren’t building bombs, that left to the sister site Aldermaston some 20 miles away.

I was fascinated by these computer things, and wrote a letter to Harwell. The letter has long since been lost, but the gist of it:

Hi my name is Simon Barrett, my mother and father run The Hare in West Hendred. I have talked to many of the scientists that stay with us. I am very interested in computers. One of them left a book, Fortran Reference Manual. I think computers are the way of the future. I would love to get involved. Do you have any jobs available?

You have to understand that this was before there were degrees in Computer Science.

About a week later I received a letter inviting me to an interview. I had never done an interview, and had no idea what to expect. In retrospect it rather reminds me of the classic movie Flashdance. I was faced with half a dozen important looking people behind desks, while I was seated on an uncomfortable chair in the middle of the room!

After some Bowler Hatted Gentleman from London visited my neighbors (to ensure I was not a soviet spy), I was in!

What a great place to work. The Dekatron was long gone, but innovation was everywhere! At the center was the biggest, baldest IBM mainframe available. Sure it did the heavy lifting, but it was the plethora of less eye popping computers that made it all possible.

The brainiacs at Harwell were decades ahead of what other people were doing. There is little doubt that HUW (Harwell Users Workshop) was the defining moment in interactive processing. It set the standard for moving from the Batch world to a more interactive world. I don’t remember how many terminals we had, but it was somewhere in the 200’s as I recall.

UKAEA Harwell is long gone. The Nuclear Reactors have been removed.

Gleep was my neighbor, we shared the same WWII bomber hanger. We were separated only by a brick wall. It was known by the catchy title Hanger Four.

Harwell is now an Industrial Park.

It is a shame, but at least the Dekatron has survived. The PDP 8, the AES 4000 that formed the backbone of HUW have not.

Personally I love the fact that the Dekatron has been revived. This was everyone’s idea of a computer, it made noise, and had flashing lights!

Simon Barrett

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