EducationObituaryAllan Nunn May
Physicist who began the atom spy eraT he physicist Allan Nunn May, who has died aged 91 in Cambridge, became notorious for passing secret information to the Soviet Union about the Manhattan project, the western allies' development of the atom bomb. Sentenced to 10 years hard labour in 1946 and released in 1952, his case opened the era of the "atom spies", led the US to end the sharing of atomic information and thus led to the British bomb. But in a curious twist, shortly before his death, the scientist told his family that he had initially contacted the Russians to alert them to the risk of the Nazis unleashing a "dirty bomb" - comprising fission products - against the Soviet Union.
The name of Nunn May - who had been working in Montreal on the Manhattan project - was disclosed by defector Igor Gouzenko, a cipher clerk at the Soviet embassy in Ottawa, Canada, in 1945. The physicist gave his contact information about the first atom bomb test as well as samples of uranium 233 and 235.
In 1942 Nunn May had been invited to join Tube Alloys - the codename of the British atom bomb project. A year later he moved to Canada - and was later recruited by Soviet military intelligence.
At his trial, he argued that he passed on information at a time when the Soviet Union was an ally. When he was released, he insisted that he had "acted rightly" and that he only passed on inform-ation because he felt it was a "contribution I could make to the safety of mankind".
Born in Kings Norton, Birmingham, Nunn May was the youngest of the four children of a brassfounder. Scholarships took him to King Edward School, Birmingham - where he was a contemporary of Enoch Powell - and Trinity Hall, Cambridge, in 1930.
Cambridge radicalised him. His most inspirational teacher was Patrick Blackett and Nunn May graduated with a first in physics. His PhD examiners were Ernest Rutherford himself and CD Ellis, who invited him to take up a lectureship at King's College, London. At KCL, Nunn May developed his own research, joined a Communist party group and became active in the Association of Scientific Workers.
By September 1939 he was working on a secret radar project in Suffolk, and at this time apparently he allowed his CP membership to lapse. That October he was sent to Bristol as part of the evacuated KCL physics department. There he met Cecil Powell and worked with him on detection of fast particles from radioactive substances using photographic methods.
N unn May became familiar with the Peierls-Frisch report, on whether a uranium U-235 bomb was feasible, in April 1940. In early 1942 he was recruited by James Chadwick to the Cambridge team working on the possible use of heavy water as the basis for a reactor. It had recently been shown that plutonium, generated in such a reactor, would be as effective as U-235 for making a bomb and that it might be easier to prepare. It was vital to know whether German work on heavy water was likely to have a successful outcome. Nunn May's previous CP membership was known, say his family, but was not seen as a bar to recruitment because the Soviet Union was an ally.
Then came the "dirty bomb" incident. Nunn May was assigned to analyse an American report that proposed that fission products could be used as poisons and delivered against an enemy. The report considered it likely that the Germans did have a working reactor and could use such a weapon either in the west or against the Soviet Union. According to Nunn May, he and others initially accepted this report as accurate in its evaluation of how far the Germans had progressed (it was later shown not to be accurate). Thus, according to him, came the fateful initial contact.
After the Gouzenko revelations, Nunn May was allowed to return to KCL in the hope that he would reveal contacts. Subsequently the press made much of the $200 he had received for his betrayal. It had been a trick, he said, and he had burned the money. But that and the cold war helped convict him.
While he was inside former colleagues saw to it that his work was published, and others maintained their friendships with him. Meanwhile, he sewed mail bags and then graduated to pay clerk. He also tutored other inmates, especially young Poles from the wartime "Anders' Army".
After release he met and married Hilde Broda, a Cambridge doctor, and returned to the city in 1953. Blacklisted until 1961, he relearned theoretical physics and eventually, it appears, he was covertly provided with a stipend for work in a private laboratory making scientific equipment. His family suspect this was to minimise the temptation to defect. His view was that he had accepted his punishment and he had no wish for exile.
In 1961 President Kwame Nkrumah invited him to Ghana as a research professor. His wife started a new medical career and they stayed in Ghana until 1978. His research was now on solid state physics. He also created a science museum.
In 1978 he went back to Cambridge. The dangers that he had foreseen of a monopoly of nuclear capability by the US - and the extreme danger of relatively easily made dirty bombs - convinced him that his actions had been justified.
He is survived by his wife Hilde, his son and stepson, five grandchildren and step-grandchildren.
ncG1vNJzZmivp6x7tbTEoKyaqpSerq96wqikaKaVrMBwfo9pamiikaN8c3%2BOoKyaqpSerq%2B7waKrrpminrK0es6boK2tkae2pr8%3D