Scientists yesterday paid tribute to Sir Joseph Rotblat, the nuclear physicist and Nobel peace prize winner who resigned from the Manhattan Project to become a campaigner for nuclear disarmament. He died peacefully in his sleep on Wednesday at his London home, aged 96.

Polish born, Rotblat started work on nuclear weapons at Liverpool University in 1939. He moved to Los Alamos, the US nuclear weapons laboratory and joined the Manhattan project, in the belief that a nuclear bomb was the only realistic deterrent against the Nazis who were also pursuing the bomb.

"In 1944, when I learned the Germans had given up the project, the whole rationale for my being there disappeared," Sir Joseph told the Guardian this year.

He became the only scientist to resign from the project and was accused by the US of being a spy.

On condition he severed all contact with other scientists on the Manhattan project, he returned to the UK to pursue medical physics at St Bartholomew's hospital in London.

Rotblat later co-founded the Pugwash conferences, a movement that worked behind the scenes, chiefly during the cold war, to discourage the use and proliferation of nuclear weapons. The group's efforts were acknowledged in 1995 when Sir Joseph and the Pugwash group won the Nobel peace prize.

"He's been an inspiration to people all over the world. He devoted his life to preventing the use, spread or existence of nuclear weapons," said Robert Hinde, chairman of Pugwash conferences in the UK and emeritus professor at Cambridge University.

The Pugwash conferences, set up after a meeting of scientists in Pugwash, Nova Scotia, invited scientists primarily from the US and the former USSR to discuss the implications of a nuclear war.

The group was the only bilateral link between the US and USSR at the time.

Rotblat remained an active campaigner until shortly before his death earlier this year, writing an open letter to President George Bush calling on him to show "courage" in implementing the treaty on the non-proliferation of nuclear weapons.

© 2005 Guardian Newspapers Ltd / UK

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