ERNIE engineers

Once Harold MacMillan had announced the  scheme, he needed a team to build the machine that would select the winning numbers.  He found it at the Post Office Research Centre in Dollis Hill, north London, where the second world war code breaker Colossus had been developed.  Led by Sydney Broadhurst, the team came up with ERNIE.

Harry Fensom, who worked under Broadhurst, was a key figure in the team who designed ERNIE. He remembers: “We knew what we were going to do from the beginning.  We did check on other random generators to see how they functioned, but they were completely useless - not really random, not random enough for our job anyway.  The people buying Premium Bonds had to be guaranteed over many, many years that they would have an equal chance of winning.”

So Harry and his team returned to some of the technology they had used on Colossus.  Each man was given a different aspect of the design to concentrate on.  “There was Eric Bubb who designed the counters and Ted Luscombe who designed the console, Maurice Ruben who worked on some of the logic parts.  I designed all the basic systems and the master control.”

Once their job was done, Harry went to St Anne's to help install and test ERNIE, along with the mathematician Stephanie Brook, then known as Steve Brook to overcome prejudice against female engineers and mathematicans, who checked the output was random.  Miss Brook is now Dame Stephanie Shirley.

Harry never had any doubt the project would be a success. “It was a straightforward to us because that was our job.  People outside thought it was marvellous and didn’t know how we came up with it, but we’d done that sort of thing before.”

Once ERNIE was settled in St Anne's it fell to engineer Jack Armitage to look after him.  Fortunately, he had been following the team in Dollis Hill as they developed the machine.

“I went down there and I sat in with these whizz-kids and they taught me all about it,” he says.  “We went through weeks and weeks of following these people around, asking them lots of questions.”

Back in St Anne's he watched the team install and test ERNIE.  “We used to watch them arguing,” he says. “They would put an oscilloscope on and say ‘look Harry do you see that pulse there' and Harry would twirl his moustache and say ‘hmmmm’.”

Once ERNIE was up and running, Jack’s main job was to keep it going, but a lot of his time was spent acting as tour guide to the droves of people who wanted to pay the machine a visit.  “They used to show them an ERNIE film, they’d sit in front of it and then they’d be invited to come up and have a look at it. They were allowed to switch it on.  The political parties always used to come to Blackpool so at conference time we would be deluged by MPs - they all wanted to come and have a look.”

Jack continued to work with ERNIE until ERNIE 2 took over in 1973.  “We never had any major failings.  We did have the odd fault of course when the machine would stop but it was generously supplied with spares.  Practically every item was duplicated so that should the master control suddenly develop a fault we could unplug it and put the spare one in, and away the draw would go again.”