Leslie Woods

Gifted mathematician with a combatively sceptical view of nuclear fusion

In calling his memoirs Against the Tide: An Autobiographical Account of a Professional Outsider, the strikingly individual New Zealander Leslie Woods, who has died aged 84, displayed considerable self-awareness. From being a fighter pilot in the second world war, he went on to become a professor of mathematics, having learnt much about the discipline literally on the wing. He then enjoyed a progress through prestigious university posts, where his robustly disputed publications on the key question of the generation of energy through nuclear fusion made his academic career as colourful and combative as his active service.

He was born Leslie Woodhead in Reporoa, a small settlement between Rotorua and Taupo in the North Island, where his father worked as a fisherman. He spent his first few years living in a tent, but later moved to more permanent accommodation in Auckland, where he attended school. His father, however, saw that he did not progress to the grammar school, preferring him instead to train as a mechanic at Seddon Memorial Technical College. There, his talent for maths was quickly spotted and he went on to become the first Seddon student to win a scholarship to Auckland University College.

Once enrolled, he decided to resign his scholarship and join the air force. His progress was hampered, though, by some confrontations with his seniors over some unauthorised aerobatics and a minor accident on a training flight. As a result, he spent part of the war in New Zealand as an instructor. In 1943 he married Betty Bayley, and saw action that led to three tours of duty and 76 missions in the Pacific, including raids on the Japanese fortress at Rabaul.

By the end of the war Les had changed his last name to Woods, apparently to spite his father, and resumed his studies at Auckland University College school of engineering, having continued his work on mathematics to a high level without instruction. His New Zealand BSc came in 1944, under a dispensation available to servicemen with almost complete degrees.

The MSc he gained in mathematics in 1947 was accompanied by the news that he had been awarded a Rhodes scholarship, which the following year took him and his family to Merton College, Oxford, enabling him to do research on computational aerodynamics in the university's engineering department. He was awarded his DPhil, on the flow of a compressible fluid about a body, in 1950, and the following year gained a first-class honours BSc in engineering from Oxford. A string of research positions followed.

He was seconded by the New Zealand defence corps to the National Physical Laboratory at Teddington, Middlesex, working on aerofoil theory. He became a senior lecturer in applied mathematics at Sydney University in 1954. Then, in 1956, at the age of 33, Les became the second Nuffield research professor of mechanical engineering at the University of New South Wales. When the Australian Mathematical Society was founded in 1956, he was elected a council member, and from 1958 to 1959 he was its vice-president.

However, in 1959 he was back in Britain with his family, to take up a post as an associate of the controlled thermonuclear reaction division of the Atomic Energy Research Establishment at Harwell, Oxfordshire. There had been many attempts to generate power by controlled thermonuclear fusion, with plasma (ionised gas) confined by magnetic fields. Les started on investigating the basic magneto-plasma problem of why, in all attempts to confine plasma, it escaped across the magnetic field at thousands of times the rate predicted.

The early optimistic forecasts of the imminence of power production by controlled thermonuclear reactions looked increasingly improbable. None the less, the project has since moved a few miles north to the science centre at Culham, near Abingdon, where the Joint European Torus (JET), the largest nuclear fusion experimental reactor yet built, has been in operation since 1983.

In 1961 Les published The Theory of Subsonic Planar Flow, an important text in applied mathematics, and became the foundation fellow in engineering at Balliol College, Oxford, retaining a connection with Harwell as consultant in plasma physics. Nine years later he became professor of mathematics (theory of plasma): it was during this period of his career, and in texts afterwards, that his combative approach manifested itself again in his quarrel with fusion physicists and his scepticism about Tokamak, the favourite device of fusion research supported by governments for more than 50 years with billions of pounds' worth of funding. His four major texts - Magnetoplasma Dynamics (1987), An Introduction to the Kinetic Theory of Gases and Magnetoplasmas (1993), Thermodynamic Inequalities with Applications to Gases and Magnetoplasmas (1996) and Theory of Tokamak Transport: New Aspects for Nuclear Fusion Reactor Design (2006) - were dismissed by some of his peers, who argued that Woods had ignored the basic principles and equations on which the Tokamak theory is based.

Regardless of his controversial approach, and his suggestion that those involved in fusion would never admit its failings so long as their livelihoods and careers depended on its "steady progress", Les gained DSc degrees at Oxford, the former University of New Zealand and Auckland - the last an honorary award during the university's centennial celebrations in 1983. His career culminated as chairman of the Mathematical Institute at Oxford, from 1984 to 1989, and in 1990 he became professor emeritus.

Les's life with Betty had mostly been happy, but in 1977 their marriage ended in divorce, as did two further marriages. Of his five daughters from his first marriage, two predeceased him, and it was through the persuasion of his eldest, Coral, when dying of cancer at the age of 49, that he wrote for her a brief account of his early life in New Zealand. She urged its expansion and publication, which duly occurred in 2000, after its rejection by two publishing houses for being rather too cutting and assertive.

Citing his pleasures as music and philosophy, Les also played the clarinet and in later life, aged 73, returned to the air when he took up gliding. As colleagues, now based in Auckland, who knew him over many years, we valued him for his friendship, sheer brilliance, and his tenacity for propagating (often unpopular) scientific truth.

Garry Tee and Graeme Wake

Leslie Colin Woods (Woodhead), pilot, mathematician and physicist, born 6 December 1922; died 15 April 2007

7 June 2007 The Guardian