Penney was the son of William Alfred Penney, a sergeant major in the Royal Ordnance Corps, who could not afford to pay for an education for his son. In fact in the early years, young William had no formal education at all; for the first 12 years of his life he lived a nomadic existence in various outposts including Gibraltar, where he was born. His father was an explosives expert, and family rumour had it that during the First World War he helped train Lawrence of Arabia in the techniques of laying charges. On their return to England, the Penney family settled in Alexandra Road, a modest row of Victorian terraces in Queensborough on the Isle of Sheppey, Kent. Penney’s mother Blanch had a head for figures and was chief cashier at the Co-op.
Penney was set for an unremarkable life until, almost by accident, his tutors at Sheerness secondary school discovered he was a mathematical genius. Exasperated teachers complained about the precocious boy who was shouting out the answers to mathematical problems almost before equations on the chalk board were finished. The tutors nurtured this unexpected savant and were not surprised when Penney obtained the highest results in all England when he sat for scholarships in mathematics and physics. His results were so spectacular they guaranteed him entry to the prestigious Imperial College London. From there he was awarded a Commonwealth scholarship, and spent two years in America at the University of Wisconsin.
On his return he was offered a place at Cambridge where he studied the magnetic properties of crystals and the structure of metals. He went back to Imperial College after obtaining a brilliant First, and picked up two doctorates on the way. Finally he was made a Professor of Mathematics at Imperial College. He was just 27 years old.
He married Adele, who lived next door but one in the tight huddle of terraced houses that formed a graceful perspective down to the sea at the bottom of the road. They married in Queensborough, had two children and eventually moved to Croydon. Adele’s clever husband was set for a distinguished academic career, but the war intervened. Penney joined a loose collection of government scientific workers, and was “borrowed” by the Admiralty to investigate a subject about which little was known: the nature of blast waves. As part of that work he made a study of underwater blast effects which was eventually used in designing the floating ‘Mulberry harbours’ to be used later in the ‘D’ Day landings.
He also had another job: under cover of working as an air raid warden, Penney was tasked by the War Office with finding out the size of the Luftwaffe’s bombs by studying the effects on the gutted remains of the buildings they destroyed. Penney’s detailed calculations enabled Army ordnance chiefs to work out the probable performance of Britain’s own bombs and missiles. There was a gruesome side to his work, however: he was required to work alongside the rescuers who brought the tragic victims of the bombings to the mortuaries. In this way Penney discovered among other things the extraordinary resistance of the human body to blast waves.
By the time that he was sent to Los Alamos the young scientist was the world authority on the effects of high explosives and blast waves on buildings and people. From backroom boy in an obscure government department, he was suddenly one of the foremost scientists of the times, and he was in distinguished company indeed. With him on his first trip to America on the converted luxury liner Andes which set off from Liverpool bound for America in late 1943, was a galaxy of scientific stars including James Chadwick, discoverer of the neutron, Rudolf Peierls, Egon Bretscher, George Placzek and Klaus Fuchs.
From New York the group, for security reasons, was separated and despatched by various modes of transport, first to Washington to be briefed on security by General Leslie Groves, the man in overall charge of the Manhattan Project. Groves (with good reason, as it turned out) deeply distrusted many of the British contingent. But for some reason he took an immediate liking to Penney. Physically they were very similar, both bulky figures with heavy facial features and a slightly rumpled look. In personality, however, they couldn’t have been more different. Penney, quiet and unassuming, was the antithesis of Groves’ bombastic deportment.
Groves appears to have recognised in Penney a kindred spirit. They both had an absolute commitment to their work and were impatient with colleagues who found the task distasteful. From their first meetings, Groves had marked Penney down as being only one of a handful of scientists he would allow into the bomb project’s innermost councils.
Los Alamos with its alien landscape and dizzying altitude was in stark contrast to Britain’s rain-soaked climate, and most of the scientists took to it with relish. Once comfortably billeted (they were overwhelmed by the plentiful supply of foodstuffs of all varieties) they threw themselves into intensive rounds of meetings and tutorials, punctuated by lively discussion groups. Music evenings and exuberant parties where alcohol and dancing flowed with equal verve were also a feature.
Christmas in Los Alamos brought with it a white blanket of snow turning the high desert shrub into a Hollywood movie set. Tinsel and other festive paraphernalia festooned every home while long icicles hung from rustic cabins giving everything a magical feel. The air was cold and crisp and the snow-capped mountains in the distance dazzled in the gorgeous sunsets. Poised as they were on the precipice of creating a monstrous, almost satanic force of nature, this outlandish and exquisite Christmas must have been a poignant counterpoint.
Penney seemed to come alive in the intellectually-charged climate and was a favourite among the American scientists for his easy-going manner and the quiet authority he showed when discussing the nature of blast waves. He stunned them with graphic descriptions of the worst effects of the bombings, all delivered in a matter-of-fact style, but with a glint in his eye and a gleaming smile. His audience was apparently so impressed that one scientist, Victor Weisskopf, nicknamed Penney “the smiling killer.” It was a moniker that stuck.
It didn’t go unnoticed that the quiet Englishman had a new, harder edge when he returned to Los Alamos after his compassionate trip to England. Gone was the shyness he displayed on first arrival, and his famous smile was not quite the same. His eyes had acquired a steely quality, and there was a firmer set to his shoulders.
Penney chose not to reveal his wife’s mental trauma, saying only that she had been killed in an air raid (Mrs Penney in fact died from pneumonia on April 18, 1945 at Warlingham Hospital). Penney brought the reality of modern warfare home to the Americans at Los Alamos who had so far only viewed events from afar. And Penney’s eyewitness account of the devastation wrought by Hitler’s latest terror weapons the V1 and V2 bombs galvanised them more than anything. These futuristic weapons with a payload of 2,000lbs of high explosive arrived completely without warning and, as Penney was keen to point out, there was no defence against it. Imagine if it could be armed with an atomic weapon!
At one colloquium Penney announced the results of his calculations on the impact of an A-bomb. A hush descended on the room as Penney, with a beaming smile, described how a city of 300,000 people would be reduced to a sink for disaster relief, bandages and hospitals. One of the people most impressed by Penney’s intensity was Philip Morrison, a 27-yr-old physicist. He described Penney’s ‘nervous smile’ as he discussed casualty numbers. “It was reality,” recalled Morrison. “We knew it, but we couldn’t see it. But Penney could.”
Just before Christmas 1944 Penney produced a memorandum in which he discusses in chilling detail the effects of the “blast resisting characteristics of German towns and those of Japanese towns.” After calculating the relative heights for the most destructive results on civilian housing from the “Gadget”, the code name for the atomic bomb, Penney moves briskly on to what is considered to be only two alternatives: a) complete destruction, or b) severe but not irreparable damage. He makes it clear in his memo, only recently declassified, which was the favourable option:-