Ross Hesketh was, like Mordechai Vanunu, one of a small band of nuclear whistle-blowers who believe that nuclear weapons should be abolished. Like most other whistle-blowers, Hesketh paid dearly for his actions. The Central Electricity Generating Board (CEGB) sacked him, specifically for making public the links between the British civil nuclear-power programme and Britain’s military nuclear programme.

Hesketh opposed any diversion of plutonium produced in civil nuclear-power reactors for military purposes. In addition, he was actively interested in a number of other nuclear issues — particularly, methods of strengthening international safeguards on nuclear materials and technologies, the World Court Project to get the use and threat of use of nuclear weapons made illegal, and the health effects of exposure of human beings to low levels of radiation.

Ross Vernon Hesketh was born in 1929 in Codnor, Derbyshire. His parents, who ran a grocer’s shop, sent him to the local Heanor Grammar School. After graduating in physics at what was then King’s College, Durham (now Newcastle University), he took a PhD, and then worked for the Falkland Islands Dependency Survey (now the British Antarctic Survey) between 1954 and 1956. Based in Cambridge, the survey, a component of the Natural Environment Research Council, conducts most of the British research on and around the Antarctic Continent.

Between 1956 and 1959, Hesketh worked as a research fellow at Glasgow University and then joined the CEGB. He first worked at the Dounreay nuclear establishment in Caithness, at which research was being conducted into the fast breeder reactor, but then went to the CEGB’s Research Laboratories at Berkeley, Gloucester. Between 1964 and 1966 he was the Research Head, Radiation Damage and between 1966 and 1983 the Research Head, Solid State Physics.

The huge increase in the number of nuclear weapons deployed by the US during the Cold War caused a shortage of plutonium in America. In 1945 the US had six nuclear weapons; in 1955, it had more than 3,000; and in 1965, it had over 31,000. Establishing this formidable nuclear arsenal required a large amount of plutonium — more than 130 tonnes. Not very surprisingly, there was a plutonium shortage in the USA.

In the 1980s there was again a plutonium shortage as the Americans, under President Reagan, brought in new types of nuclear weapons and maintained a nuclear arsenal of about 23,000 nuclear weapons. Hesketh suspected that plutonium from British civil nuclear-power reactors (Magnox reactors) was being supplied to the USA for use in nuclear weapons.

The plutonium produced in the early years of the operation of Magnox reactors is ideally suited for use in nuclear weapons. Hesketh began publicising his suspicions, starting with a letter to The Times on October 30, 1981. This publicity greatly embarrassed the British Government. In 1983 Hesketh was sent on leave for a few months and then fired by the CEGB, a publicly owned body. But he continued to expose the diversion of plutonium produced in British civil reactors to military use and its export for the same purpose.

In 1985 Hesketh joined Bayero University in Kano, Northern Nigeria as Professor of Physics and dean of the science faculty. He proved to be an excellent teacher who filled his Nigerian students with enthusiasm. In 1989 he moved to Sultan Quaboos University, in Muscat, Oman. In 1991 he retired to England.

In an article in mid-1999, Hesketh publicised the American admission that under the US-UK agreement for “Cooperation on the Uses of Atomic Energy for Defence Purposes”, known as the Mutual Defence Agreement, it received 5.4 tonnes of plutonium for its weapons programme between 1960 and 1970, enough for about 1,300 nuclear weapons. Britain’s civil (non-military) nuclear programme began in 1962, when nuclear power reactors at Berkeley and Bradwell went into operation. Hesketh pointed out that the 5.4 tonnes of plutonium sent to the USA accounted for “the entire production of plutonium from all the UK civil nuclear power stations, up to April 1969, according to official sources”.

No British government, including the present one, has been willing to admit that plutonium produced in British civil reactors has been used for military purposes. The Government and the nuclear industry have consistently denied that the civil and military nuclear programmes are linked. However, in March 1986 the chairman of the CEGB, Lord Marshall of Goring (who died in 1996), did concede that plutonium from the early Magnox civil reactors had been diverted to Britain’ s military nuclear stockpile.

Hesketh became very interested in the health effects of low levels of ionising radiation — alpha, beta and gamma radiation emitted by radioactive isotopes. He was particularly interested in the health effects when the radioactivity is inhaled or ingested into the body; he gave the issue a great deal of thought and wrote articles on it. The topic has been very controversial for several decades and is likely to remain so for years to come.

Hesketh argued that the worldwide health effects resulting from the nuclear accident at the Chernobyl reactor in August 1986 were underestimated, particularly by the world’s nuclear industry. In 1996 he wrote: “In the US, data from 32 states show an increase in newborn hypothyroidism arising from Chernobyl, in Provence-Alpes-Côte d’Azur thyroid cancer in children has increased by a factor of six and in Wales an increase in low birthweight in 1987 is beyond dispute”. This and much other evidence convinced him that “low-dose rate irradiation is more damaging than the nuclear industry would have the world believe”.

In other words, he argued that the risk factors used by the official bodies are based on inadequate modelling so that more damage to health is done at low doses of radiation than the models predict and less damage is done at high doses. This may be particularly so for young people and individuals genetically susceptible to radiation damage.

In today’s world, people are being increasingly exposed to ionising radiation from the use of radioactive materials in industry, medicine and agriculture. Hesketh argued, therefore, that larger “research funds should go to the groups, or individuals, who do work of high quality” on the health effects of low levels of ionising radiation.

Ross Hesketh, a committed Quaker, was an unusually private man. Nevertheless, a large number of people attended his funeral, an indication of his wide range of activities and interests. Music meant a lot to him. He played the harpsichord well and built viols, medieval six-stringed musical instruments. The continuity of music over the centuries appealed to him. His other hobbies were climbing and photography.

His wife Elva, two sons and two daughters survive him.

Ross Hesketh, physicist, was born on April 5, 1929. He died on April 3, 2004, aged 74.