The independent nuclear deterrent and the Thames flood barrier are just two of the wildly dissimilar projects he promoted in a career that took him from internment as an enemy alien during the second world war to the top of the civil service via leadership of the European Space Research Organisation, later to become the European Space Agency.
He was also a first-rate academic whose mentoring qualities saw him labelled the "supervisor's supervisor", a witty and energetic teacher whose Cambridge lectures, according to fellow academics, were a tour de force. He could give almost his entire course on mathematical physics without notes. He was appointed master of Churchill College, Cambridge, in 1983 a post he held until 1990.
Bondi's early reputation - some might say notoriety - came as a member of the "Cambridge Circus": Fred, later Sir Fred, Hoyle, Thomas "Tommy" Gold, and Bondi himself. The three young scientists, led by the irrepressible Hoyle, developed what became known as the "steady state" theory of the universe. They argued the cosmos was immeasurably old: that it had neither origin nor would have an end and that matter was being created continually to replace matter lost to the far reaches of outer space.
In the end, the "Big Bang" theory, which holds that both space and time began in an explosion 14 billion years ago, has been accepted by most cosmologists. Bondi had the flexibility of mind and lack of dogmatism to see the weight of evidence lay with the Big Bang theory. His own work had, in any case, made his name, transforming our understanding of the way stars are affected by interstellar clouds and gravitational fields.
Bondi was born in Austria of Jewish parents and brought up in Vienna. His father was a doctor. He was educated at the Vienna Realgymnasium and showed precocious mathematical ability but was troubled by the increasing anti-Semitism of the time. Encouraged by the eminent UK astronomer Sir Arthur Eddington, he applied to and was accepted in 1937 by Trinity College, Cambridge. Within six months, his family fled to Switzerland then to the US before the Hitler onslaught. Bondi, however, stayed in England where in 1940 he was in-terned and met his fellow Austrian Jew Tommy Gold. The two became and remained firm friends.
Released after 15 months, Bondi worked with Hoyle on radar research where they were joined, on Bondi's recommendation, by Gold. Bondi carried out fundamental research on the physics of the magnetron, the device at the heart of radar systems and, these days, microwave ovens. With Hoyle and Gold, he contributed to a period of remarkable creativity in theoretical astronomy at Cambridge.
Bondi was appointed professor of mathematics at Kings College, London, in 1954 and in 1959 at 40 a fellow of the Royal Society. In 1967 he became director-general of the European Space Research Organisation and, in 1971, chief scientific adviser to the Ministry of Defence. He became chief scientific adviser to Tony Benn at the Department of Energy six years later. Forced by civil service rules to relinquish the post at 60, he became chairman of the Natural Environment Res-earch Council.
Bondi was naturalised in 1946. Initially an outsider but with a burning desire to belong and contribute, he achieved more than he could have hoped for in his adopted country. He was knighted in 1973. He met Christine Stockman, one of Hoyle's graduate students, while both were seeking a meeting with the elusive astrophysicist and married her in 1947. She survives him as do their three daughters and two sons.
Obituary by Alan Cane
Hermann Bondi, scientist and civil servant, born November 1, 1919, died September 10, 2005.