His falling out in 1977 with Tony Benn, then Minister for Energy, led to him being sacked from his post as Chief Scientist at the Department, and was one apparent setback in his pursuit of this cause. In reality, that event, which at the time caused him considerable grief but which he came later to realise made him persona grata with the incoming Thatcher administra-tion, shows Marshall in a more intriguing light. For the trigger for his dismissal was not nuclear power, but the Minister's concern about how the poor were to meet their energy bills.
Taxed with this problem, Marshall wryly observed that perhaps the answer might lie in providing the poor with money, or failing that coin-like tokens bearing the profile of Benn's head. A sharp wit and effervescent sense of humour were formidable weapons in Marshall's armoury, and help explain the extraordinary affection he could command among his colleagues, companions and staff despite his ability also to make enemies.
He was a man big enough physically as well as intellectually to be worthy of caricature, and he would happily exploit this in Johnsonian style by poking fun at himself. Thus on public platform and in after-dinner speech, not only was he a lucid and vivid exponent of the abstrusest technical issues, but he could reduce an audience of the dullest engineers, the most pompous businessmen and self-important politicians to helpless laughter with exquisitely timed Hoffnungesque stones. Here he deployed his larger- than-life personality with its unapologetic egocentricity, his tortured vowels born of humble Welsh origins and brilliant university education in Birmingham from central European tutors, and his great sense of theatre.
Indeed, Marshall's whole career was a high-wire act, combining showmanship and skill. A First in Mathematical Physics from Birmingham University at 20 was followed by a PhD at 22 and election as a Fellow of the Royal Society in 1971. He became head of the Theoretical Physics Department at the Atomic Energy Research Establishment at Harwell in 1960 and Chief Scientist at the Ministry of Energy in 1974. In 1981, he was appointed Chairman of the Atomic Energy Authority by Margaret Thatcher and knighted in 1982, shortly after she switched him to become Chairman of the Central Electricity Generating Board (CEGB). A life peerage followed in 1985 on successful completion of his crusade to "keep the lights on" no matter what moves Arthur Scargill's striking miners made against the power stations.
Two episodes whilst at the CEGB showed Marshall at his very best. Anticipating the NUM strike in 1984-85, he took a strategic decision to prepare the CEGB in terms of fuel reserves, people and logistical planning to ensure security of electricity supplies. And when the time came, his communications to the Government of the day were robust, detailed and reliable, whilst in the public arena he played down the CEGB's decisive role so as to avoid dragging the organisation into what would become a highly politicised dispute.
Then when a year later the Chernobyl nuclear power station fire showed the disastrous consequences of getting nuclear power wrong, it was Marshall who, leading again from the front, identified the design and operating flaws in the Russian reactor type, and bent all his powers of communication to explaining to professional and lay audiences what had gone wrong and what the essential differences were between the Russian and Western concepts of nuclear safety management.
Out of this disaster, and Marshall's prodigious efforts in response, was eventually born the World Association of Nuclear Operators (WANO), of which Marshall became the first Chairman, which for the first time embraced the Soviets in a peer-review group that has since done much to improve safety and operating performance by nuclear plants worldwide. Arguably this could be his most enduring contribution.
For Marshall himself, however, Chernobyl marked the downward turn in his fortunes. Public confidence in nuclear energy ebbed away. He lost badly when he attempted to resist on technical grounds Cecil Parkinson's politically-driven need to break up the CEGB as a prelude to the privatisation of the electricity industry. And finally he was forced to resign as Chairman of National Power (one of the CEGB successor bodies) - again in great bitterness - when the Government decided, late in the day in 1989, to withdraw the nuclear stations from the planned privatisation. The break point was the treatment of the historic liabilities for reprocessing spent nuclear fuel and decommissioning nuclear power plants. Marshall had argued all along that these would not be financeable and he carried the can for proving to be right. He felt humiliated and betrayed: he was loyal to a fault and naive in expecting reciprocation; and he had put too much faith in purely technical argument and not understood that the rest of the world sees other imperatives.
Flung from office, Marshall continued with his international work where he was hugely respected both for his intellect and as a man, particularly in Japan for which he had a particular affection and love of its food. He also worked in insurance and as a consultant, but he never recovered his previous visibility.
Throughout his life, Marshall was characterised by his relentless energy of mind and curiosity of spirit. He relished intellectual debate, and spent many hours at night and long journeys pursuing the proof of mathematical theorems. He practised origami and laboured to great effect in the garden of his Thames-side house at Goring. In all his doings, his childhood sweetheart and then wife, Ann, was his constant companion and support, at work and play. Their teamwork was legendary, as was their hospitality.
Walter Charles Marshall, physicist, public servant: born Rumney, Cardiff 5 March 1932; Head, Theoretical Physics Division, AERE 1960-66, Director 1966-75; FRS 1971; CBE 1973; Chief Scientist, Department of Energy 1974- 77; Director, Research Group, UKAEA 1969-75, Deputy Chairman 1975-81, Chairman 1981- 82; Kt 1982; Chairman, CEGB 1982-89; created 1985 Baron Marshall of Goring; Chairman, WANO 1989-93; married 1955 Ann Sheppard (one son, one daughter); died London 20 February 1996.Reuse content