By Roland Pease
BBC radio science unit
"To Britain - a Sun is Born", "H-power everlasting", "A triumph as great as the Russian Sputnik"... just some of the headlines to greet the announcement of the British Zeta nuclear fusion experiment 50 years ago on 25 January 1958.
The experiment promised to tame the power of the Sun - or the hydrogen bomb - and to make it possible to generate electricity using hydrogen from the sea, in 20 years according to most of the papers.
Journalists had been invited to the UK's nuclear research establishment AERA Harwell just days before to see the miraculous Zeta for the first time.
A hollow aluminium doughnut, or torus, three metres across, Zeta had been running in secret since the previous summer, heating gases to 5 million degrees, a third of the temperature at the centre of the Sun, in the hope of creating nuclear fusion reactions.
Currents of 200 000 amps were used to heat the gases, in pulses lasting just a few thousandths of a second.
The experiments looked like a great success, and the fanfare that followed was tremendous, spiced up by a utopian belief in the power of science - largely untainted by the cynicism that developed in the 1960s - and by national pride.
The Zeta scientists were described as "the atom men who won Round One in the race with the scientific big brothers, Russia and America".
This was "a triumph as great as the launching of the Russian Sputnik", the Daily Mail told its readers.
"Britain was faltering on the world stage," explains science historian Jon Agar of University College, London.
"The Suez crisis in 1956 made it very clear that Britain was no longer a world power. One thing they could do was celebrate the achievement of science and technology.
Zeta: For a short while it seemed the answer
"Zeta was one example of that; the Jodrell Bank radio telescope was another. This was Britain's great public spectacle of science."
Unfortunately, the claims at the Zeta press conference went too far.
It was already known that heavy hydrogen (or deuterium) atoms accelerated in electric fields and collided together would fuse and release a tiny amount of energy.
That was how the nuclear process had been discovered in the 1930s; but that process would always consume power, not generate it.
What was needed was a hot gas of deuterium, with countless trillions of nuclei whizzing around, to change the energy balance.
Only this thermonuclear fusion could be scaled up to a reactor. The scientific paper describing the Zeta results was non-committal. So were the prepared statements at the press conference.
More experiments were needed to see what kind of fusion was going on inside Zeta. The assembled press were not satisfied by this prevarication.
"I think what the press couldn't get their heads around was the fact that the scientists didn't know," recalls Dr Alan Gibson, a veteran of the original experiments.
"It wasn't that they wouldn't tell them, they didn't know, and that was a foreign concept."
Eventually, the director of AERA Harwell, Sir John Cockroft cracked, and confessed that he was 90% certain there was thermonuclear fusion.
"It was a reasonable, honest estimate," says Dr Gibson, "but the journalists took it as gospel. If Sir John thinks they're thermonuclear, they must be thermonuclear."
Thus the Zeta myth took wing; and when the more detailed analysis showed that in fact the reactions were not thermonuclear, the fall was all the harder.
The Joint European Torus has taken fusion a step forward
Instead of being a British triumph, Zeta was soon being called a fiasco, a blunder, an embarrassment.
But for the Zeta scientists, the thermonuclear reactions were not the most important thing - obtaining the high temperatures and controlling the hot gas was the technical challenge; controlled fusion could come later.
My father, Bas Pease, was on the team, and often spoke of the ups and downs of the experiment's fortunes. In 1992, on the BBC's Horizon programme, he made it clear he was in no way embarrassed.
"The more I look back on Zeta, the more I think it was a great pioneering experiment. It broke into completely new ground, and laid the foundation for the experiments we went on to do."
Dr Gibson is equally forthright: "[Zeta] was a huge success. It was technically successful. It was the predominant machine - certainly in Britain, maybe in the world for 10 years. It developed the techniques that were used in machines many years afterwards. But it was unfortunately a public relations disaster."
The expectation of press and public could not be met
Nevertheless, taming the hot hydrogen gases sufficiently to produce thermonuclear energy has proved a phenomenally difficult task.
The true "Zeta moment" eventually came in 1991, at an experiment not far from Harwell in Oxfordshire.
Researchers at the Joint European Torus (Jet) at Culham, held gases at 100 million degrees for periods of two seconds, and generated a peak energy of two megawatts. Six years later, repeat experiments raised this to 14 megawatts.
These figures are still far short of anything that could contribute to the grid, but the experiments laid the groundwork for the next international collaboration: Iter (the International Thermonuclear Experimental Reactor) currently being built in southern France.
Many observers remain sceptical that fusion energy will ever satisfy our energy needs; "success" has always been "20 years away" or more. And the sceptics argue that money spent on it is wasted, when easier goals like solar and wind energy remain to be fully developed.
But having lived close to many fusion scientists throughout my youth, and having met them again recently, I'm convinced those doing the work believe the ultimate target is worth striving for.
The fuel for fusion is heavy hydrogen from the sea and, as the paper headlines stressed 50 years ago, two grams of it can yield as much energy as 10 tonnes of coal.
ITER - NUCLEAR FUSION PROJECT
Fusion is the nuclear process that operates at the core of the Sun
Project estimated to cost 10bn euros and will run for 35 years
It will produce the first sustained fusion reactions
Final stage before full prototype of commercial reactor is built
In the words of Bas Pease: "The important thing about fusion is that it will last for ever.
"It's a source of energy from hydrogen which is distributed all over the world, so that the fuel will be available to everybody.
"It's limitless. Once it works, it really will solve an energy problem for ever."
You can listen to Britain's Sputnik on BBC Radio 4 on Wednesday 16 January at 2100 GMT. You will also be able to hear the programme later on the BBC Radio 4 website.