Sir Joseph Rotblat

Driving force of the disarmament group Pugwash and Nobel Peace Prize-winner

Probably more than any other individual, Joseph Rotblat deserves to be called the conscience of science in the nuclear age. A physicist who walked out of Los Alamos before the first atomic bombs were completed, he went on to win the Nobel Peace Prize for his inspired and unrelenting efforts to secure nuclear disarmament. His life's work was to mobilise fellow scientists in the cause of peace, as he believed they had unique responsibilities deriving both from their special knowledge and from the role of science in creating nuclear weapons in the first place.

In the 1950s he played an important role in alerting the world to the global dangers of radioactive fall-out and he subsequently helped found and lead the Pugwash organisation, promoting new ideas for disarmament, often to the irritation of governments in both East and West.

Although he lived in Britain for most of his life, an exile from his Polish homeland where his wife died in the concentration camps of the Second World War, Rotblat remained little known to the British public until the award of the Nobel Prize in 1995. But in the world of science, both as a practitioner and as a campaigner, he had long enjoyed international standing.

Joseph Rotblat was born in Warsaw in 1908, the fifth of seven children of a prosperous Jewish paper merchant and his wife. Joseph's early years were spent in some luxury, but things changed very abruptly with the outbreak of the First World War, when the family business was ruined by the closing of frontiers and the requisitioning of its horses for the army. The Rotblats fell into poverty and even hunger, and at one stage they survived by selling vodka distilled illegally at home.

Peace in 1918 brought little relief, indeed the family's fortunes never recovered, and young Joseph eventually trained to be an electrician. By night, however, he studied for a university physics degree and in the early 1930s was accepted to do research at the Warsaw Radiation Laboratory.

This was still the age of "string and sealing wax" in nuclear science, and Warsaw's facilities were primitive. Joseph Rotblat used later to recount how he conducted experiments involving two pieces of equipment kept on different floors, which meant hurling himself down flights of stairs to complete his observations in time. Only when he developed stress fractures in his legs was he given more apparatus.

In 1939 Rotblat received two invitations to study abroad, one from Paris and one from Liverpool University, and despite the strong Polish connection with Paris (through Marie Curie) he chose the latter. The Nobel Prize-winner James Chadwick was building a "cyclotron" particle accelerator in Liverpool and Rotblat wanted in due course to create one in Warsaw.

By now he was married, to Tola Gryn, a literature student whom he had met in 1930, but he travelled to England alone because he could not afford to support her there. Before long, Chadwick gave Rotblat a fellowship, doubling his income, and in that summer of 1939 the young Pole returned home meaning to bring his wife back with him. When the time came to leave Warsaw in late August, however, she was ill and remained behind, expecting to follow within days, and so once again the outbreak of war brought calamity. Tola was trapped, and all Joseph's desperate efforts in the ensuing months to bring her out through Belgium, Denmark or Italy came to nothing, as each country in turn was closed off by the war. He never saw her again.

At Liverpool University, meanwhile, Joseph Rotblat soon found many of his colleagues vanishing to do secret war work, mostly on radar. He himself was also wrestling with a war project, though not one with government blessing. Like many nuclear physicists, he had been alarmed by the discovery in Germany on the eve of war that uranium atoms were capable of "fission", a splitting process that released energy. Follow-up work quickly suggested that this was unlikely ever to be useful in weapons, but Rotblat was one of a minority of scientists who remained unconvinced and, with Chadwick closely following his work, he began to investigate the subject himself.

Two other scientists, Rudolf Peierls and Otto Frisch, were pursuing a similar line of thought at Birmingham University, and in the event it was they who crystallised the matter, producing in the "Frisch-Peierls Memorandum" of 1940 the first blueprint for an atomic bomb.

The memorandum set in motion a much bigger British feasibility study into which Rotblat's work was drawn, and in time all of this was merged into the Manhattan Project to design and build the bomb in the United States. The heart of the project was the Los Alamos laboratory in New Mexico and Rotblat was wanted there, but there was a delay because the Americans were insisting that all the British team, which included a number of refugees, should have British citizenship. Rotblat, still meaning to return home after the war, refused to renounce his Polish nationality. That it was the Americans who eventually had to relent is evidence of the man's stubbornness.

Although in scientific terms he made no significant contribution to the work on the atom bomb - indeed, he complained at times of having nothing to do - for him, as for so many others, that time at Los Alamos was the pivotal experience of his life. Arriving in March 1944, he soon felt ambivalence about his involvement. On the one hand, he had served notice that he wanted to return to Poland as soon as possible and on the other, he was more troubled than most about the morality of working on a weapon of mass destruction.

These moral doubts grew as time passed. He wrote later that he had been shocked to overhear a senior American official claim that the real purpose of the bomb was to gain dominance over the Russians after the war, and also that he was convinced of the danger of a post-war nuclear arms race by conversations at Los Alamos with the Danish physicist Niels Bohr.

His initial rationale for being involved, which he shared with many others, was a fear that the Germans might develop the bomb first and, towards the end of 1944, as it became clear that this was not a danger, his reservations increased still further. At the same time, of course, Germany's defeat was becoming steadily more likely, and his desire to go and look for his wife and for the rest of the Rotblat family was also strong.

With these doubts and worries in mind, at the end of 1944 Rotblat asked to leave the laboratory and was grudgingly given permission. He was one of only two scientists to quit Los Alamos in this way. Before he could go, however, he had to clear himself of a charge of espionage. Security staff had compiled an inch-thick file on him, brimming with tales of security breaches and including one suggestion that he intended, on his return to Europe, to parachute into Russia with the secrets of the bomb.

Behind this lay a lot of fantasy and a few unsensational facts. On visits to nearby Santa Fe, he had befriended a young Englishwoman who was in New Mexico for treatment for a hearing problem. Evidently Rotblat had been more open about his work than he should have, and she had been equally indiscreet, discussing him with a friend. This friend, a Santa Fe woman with a gift for embroidery, convinced herself and the security agents that the Pole was up to no good.

Eventually he satisfied the authorities that he was not a Soviet agent, and left. Unable to reach Poland, however, he was still in Liverpool in August 1945 when he heard the news of Hiroshima, at which point his life's great mission began.

At first he worked through the Atomic Scientists' Association (ASA), set up early in 1946 to educate British public opinion about matters nuclear and to make the case for international control of atomic energy. Rotblat was very soon at the heart of matters, organising, fund-raising and speaking. He was the dynamo behind the ASA's most ambitious project, the Atom Train, a touring exhibition which proved a popular success. It told of the dangers of the new nuclear world and the potential benefits in terms of energy and medical treatments, and asked in conclusion: "Which is it to be?"

Events soon gave their answer, as the Cold War and the nuclear arms race began, and the ASA swiftly became marginal. Rotblat's own life also moved on. Although his wife was dead, against the odds several members of his family, including his mother, survived the Holocaust. They wanted to move to Britain and, to help make this possible, he finally abandoned his hope of returning home and adopted British citizenship.

His scientific career, too, entered a new phase. In 1949 he left Liverpool for St Bartholomew's Hospital in London, swapping particle accelerators for a quite different field of study, health physics. Though many of his old colleagues told him he was mad, he made a resounding success of it, completing in the years that followed a series of landmark studies with Patricia Lindop on the effects of high-energy radiation on mice.

It was the issue of global fall-out that made Rotblat a figure of international importance, and the key event came in 1954, when an American H-bomb test in the Pacific showered radioactive dust on a Japanese fishing boat, the Lucky Dragon. All those on board required hospital treatment and one subsequently died. Looking at the evidence, Rotblat deduced that the bomb had been a three-stage weapon in which the essential fusion reaction was not only initiated by a fission explosion, but was followed by one as well. This meant that it was vastly more "dirty" than the public had been told, and when Rotblat after some delay published this fact there was uproar.

As concern grew about fall-out, Rotblat became involved with Bertrand Russell in the search for ways to end testing and ultimately remove the threat of nuclear war. He played an instrumental role in the publication of the "Russell-Einstein Manifesto", which called for an international conference of scientists to this end.

Rotblat was soon approached by a Canadian millionaire, Cyrus Eaton, who offered to host such a conference in his home town of Pugwash, Nova Scotia. So it was that 22 leading scientists, including notably a vice-president of the Soviet Academy of Sciences, gathered there in 1957 to discuss peace. Since then there have been more than 200 Pugwash conferences in many cities, all of them observing the same principles: those present represent only themselves, and their discussions are confidential.

The organisation's influence is thus hard to measure, though few would question it. At times, such as the early 1980s after the Soviet invasion of Afghanistan, it kept open lines of communication when the Cold War was at its coldest. At other times it created new lines - it was Pugwash that provided the first link between Henry Kissinger and the North Vietnamese, as early as 1967.

Above all, it provided a forum for discussion that stood outside East-West conflict, making possible new analyses of the nuclear stand-off and of the ways in which tension might be reduced and calamity avoided. In time these ideas found their way into public debate and sometimes government policy. Its independence, however, attracted suspicion and occasionally it was denounced as a stooge organisation by one side or other.

Down the years, as Secretary, Chairman and then President, Rotblat remained the driving force of Pugwash and his office, first at Bart's and later in Great Russell Street by the British Museum, was the hub.

Lean and handsome even in old age, and with a strong Polish accent and old-world manners, he could exercise enormous charm, but behind it always lay an indomitable determination, even ruthlessness. It was said of him that he was a great man to have on a committee, provided he was on your side, for he had a prodigious memory and there was nothing he did not know about the tricks of procedure. The story is also told of an Israeli scientist late with a paper for a Pugwash publication, who unwisely paid a visit to Rotblat and found himself locked in a small room until the article was complete. Rotblat's own work rate was phenomenal, running to hundreds of books, pamphlets and articles, and it is no surprise that he had little in the way of a private life, never remarrying and living quietly and modestly in north London.

In 1995, 50 years after Hiroshima, all this work and achievement was finally honoured when he and Pugwash were together awarded the Nobel Prize, and for the first time Rotblat, who always thought himself a rebel and an outsider, enjoyed the public recognition and acclaim that were his due. Three years later, long after the honour was due, he was knighted.

Brian Cathcart