Obituary: Bill Moyce

Bill Moyce was an important member of the team that built and tested Britain's first atomic bombs in the late 1940s and early 1950s and he remained at Aldermaston in a variety of senior positions all his career. He was a versatile scientist and an able manager, but he was perhaps most notable for his unflappability and for his good- humour, qualities tested to the limit in those early atomic days.

In 1952, for example, it was Moyce who was chosen to fly out to Australia with the plutonium core which was to be used in the first British nuclear test. This was without doubt the most valuable object in the country - Sellafield and Aldermaston had been built to make it - and there was natural concern about its safe-keeping. Moyce was told that if during the flight out it looked as though the RAF plane was going to crash, he was to clutch the container in his arms, bail out and descend by parachute. It was fortunate that this proved unnecessary, for, as he recalled later, he had never made a parachute jump and it was his first flight in an aeroplane. He was also very doubtful about his ability to hold on to it at the moment the parachute opened.

William Moyce was born in Brockley, south-east London, in 1913. His father, a Fleet Street printer, taught him to set type, but he had other ambitions. From grammar school he won a scholarship to Downing College, Cambridge, graduating in Natural Sciences in 1934. A year later he landed his first job, at Woolwich Arsenal, and he was to spend his entire career in armaments science.

He spent the war in the Potteries, at an outstation of Woolwich devoted to improving the performance of small arms, and it was there, in late 1946 or early 1947, that he caught the eye of William Penney, the father of the British bomb. It is a measure of Penney's shrewdness that he saw Moyce's genuine talent behind his rather lugubrious manner and his oddly drawling south London delivery.

Initially, Moyce worked at Fort Halstead, Penney's headquarters near Sevenoaks in Kent, on what was called the "phenomenology" of nuclear weapons, that is, studying the processes that took place in the course of the explosion. As the pressure grew to make the atomic bomb, however, he was transferred to more applied work and given the job of designing and supervising criticality experiments. An atomic bomb works by combining two pieces of plutonium which, while separate, will not explode, but when forced together violently achieve the "critical mass". The margins are tight, and it was Moyce's task to see that they were observed.

Aubrey Thomas, a junior member of Moyce's team who also died recently, told me: "Moyce was trained as a physical chemist, and at first he didn't know the difference between a neutron and a little black ball. But in 18 months he knew so much that he was arguing, on visits to Harwell, with some of the leading physicists in the country. He had a childlike mind; so clear, always asking the awkward question. He could span all science without apparent effort."

In September 1952, at Aldermaston, the first hemispheres of the plutonium core of the bomb were cast, and Moyce and his men spent a tense 20 hours verifying that they could be combined without risk of a premature explosion. They had constructed a giant rig, ringed with neutron counters, which brought the two halves close together, millimetre by millimetre, until they touched. The counters were there to give warning of premature criticality, although if there had been a genuine accident any warning would almost certainly have come too late and some or all of those present would have died.

There were no accidents; the core was safe, and Moyce took it to Australia.

The bomb was placed in a redundant frigate, HMS Plym, and, early in the morning of 2 October, Moyce supervised the loading of the core into the huge high-explosive jacket - a great ball almost five feet across whose job was to crush the plutonium and precipitate the explosion. Again, this was a millimetre-by-millimetre job with counters clicking away all the time. Eddie Howse, a colleague, has recalled pacing up outside the bomb room listening to Moyce's voice from within saying: "Slow . . . slow . . . readings going up . . . stop . . . wait . . . go down . . ." This operation took 90 minutes.

The test, called Operation Hurricane, was a success, and Moyce's future in the nuclear weapons business was assured. Like many of that first generation - now sadly dwindling in numbers - he remained at Aldermaston for the rest of his career, playing a part in all the great projects: the H-bomb, Polaris, WE-177, Chevaline. For much of this time he was in charge of the explosives division, which supplied the conventional explosive element for warheads. This was an exacting field, given the continuous demand for smaller, lighter and more efficient weapons.

Moyce's tasks were by now largely managerial, but he never lost his scientific insight or his knack of asking the penetrating question. Pat Cachia, who worked for him in explosives, recalls: "He was a free-thinking scientist. Without getting too involved in detail, he made contributions in every area which were fundamental and deep."

Moyce finished his career in 1973 as head of safety at Aldermaston. He was a tall man with big ears and a slightly gloomy air, an appearance which proved a great complement to his comic gifts. He was the joker of the team, with a dry London wit and the gift of telling a story. In retirement he devoted himself to gardening. He is survived by his wife Barbara, whom he married at the time he joined the bomb project in 1947, and his son John, who was born within a week of the 1952 Hurricane test.

William Moyce, nuclear weapons scientist: born 12 October 1913; OBE 1963; married 1947 Barbara Manson Campbell (one son); died Newbury 6 September 1996.