Obituary: Professor R. V. Jones

Reginald Victor Jones, physicist: born London 29 September 1911; Scientific Officer, Air Ministry 1936-39, Air Staff 1939-41, Assistant Director of Intelligence 1941-46, Director of Intelligence 1946-52; CBE 1942; Professor of Natural Philosophy, Aberdeen University 1946-81 (Emeritus); Director of Scientific Intelligence, Ministry of Defence 1952-53; Chairman, Air Defence Working Party 1963-64; FRS 1965; CH 1994; married 1940 Vera Cain (died 1992; one son, one daughter, and one daughter deceased); died Aberdeen 17 December 1997.

R. V. Jones was one of the main wizards during the secret war against Hitler, became a pillar of scientific education, and wrote some notable books.

His father was a sergeant-major in the Grenadier Guards, and from him he learnt both patriotism and a sense of order. He went to Alleyn's School at Dulwich, from which he won an exhibition at Wadham College, Oxford, where he distinguished himself so much that he was encouraged to stay on, to take a doctorate in physics and to research under the future Lord Cherwell in the Clarendon Laboratory. He specialised in infra-red rays, and spent the years 1934-36 at Balliol, as Skynner Senior Student in Astronomy; but then moved over to deal with the more pressing problems of the German menace. He was made a scientific officer at the Air Ministry in 1936, and was seconded for a year to the Admiralty in 1938-39. In both departments he applied a first-class scientific intellect to practical problems of warfare.

When the Second World War began, he became MI6's principal scientific adviser; keeping up his Air Ministry connection for cover. His first important task was to discover how Luftwaffe pilots navigated when they overflew England by night, during the Battle of Britain and the blitz. He unravelled the Lorenz beam navigation systems they were using, and was sometimes able to jam, sometimes to divert their beams. On the night of the Coventry raid in mid-November 1940, Jones guessed correctly which wavelength they would be using; a clerical error transmitted the guess wrongly to the jamming stations, and so helped to account for the raid's success.

It was Jones who briefed the RAF expert who dropped by parachute on to the Bruneval radar site, in February 1942, to dismantle a German radar device and bring it back for inspection. It was Jones who, after years of struggle, convinced Bomber Command that pilots who left their IFF (identification friend-or-foe) sets switched on over Germany guided German night fighters on to themselves. It was Jones who played a leading part in discovering what the V-1 and the V-2 were, and how they might best be countered. Several times over, he found himself confronted by Winston Churchill, in meetings of ministers and experts; even Churchill's personality was not so strong that Jones fell silent in his presence. By standing up to him, he helped to persuade him to give orders on which the nation's safety turned; though of course he earned enemies for himself among the bureaucrats of Whitehall.

Jones could not work usefully unless he was privy to every secret. He was cleared to receive messages from the ultra secret decipher service at Bletchley Park; he was cleared to read spies' reports, as they were received, not in the laundered form in which they reached lesser intelligence officers; he knew a great deal both about impending operations and about the current organisation of the armed forces, the air force in particular. He knew work was in progress on an atomic bomb. He was a large man, broad- shouldered and over six feet tall, with a strong voice when he cared to raise it. Moreover, he had a disconcerting habit of usually being in the right, as well as displaying admirable manners when he was in the wrong - as of course he sometimes was.

As soon as he was released from National Service, he was snapped up by Aberdeen University, where he spent 35 years as Professor of Natural Philosophy, teaching generations of undergraduates and research students who appreciated his wit, his knowledge, and his enormous fund of common sense. He was fond of quoting Crow's Law - "Do not believe what you want to believe until you know what you ought to know."

When Churchill came back into office in 1951, he tried to recall Jones to Whitehall; an embarrassed year in 1952-53 as director of scientific intelligence at the Ministry of Defence resulted. Long afterwards, Jones explained that intelligence could not usefully be organised in committees of fairly senior officers who knew nothing about the subject in detail; and he left official life for academic. He did notable work for the Royal Society, and belonged to institutes and academies for the promotion of electronic research, almost without number. He wrote numerous scientific papers, and papers on the history of science, as well as two remarkable studies in the practice of his wartime craft: Most Secret War (1978, called in America The Wizard War); and Reflections on Intelligence (1989). They are much the best and fullest books ever to have appeared on the wartime secret service's workings.

At the age of 80, he lost in a fortnight his wife of over 50 years and one of his daughters; he went on writing learned articles all the same, a model to younger scholars of devotion to even temper, good-humour and scientific truth.