B Nov 29 1912, died Monday 26 June 1995

See also an obituary in the New York Times.

BRIGADIER SIR EDGAR "BILL" WILLIAMS, who has died aged 82, was a brilliant Chief of Intelligence to Montgomery in 21st Army Group and subsequently had a glittering academic career as a Fellow of Balliol College, Oxford, Warden of Rhodes House and Editor of the Dictionary of National Biography.

In August 1942 General Montgomery took command of the 8th Army. "I discovered there," he recalled, "a major in the Intelligence Branch in the King's Dragoon Guards by name Williams, an Oxford Don and had a brilliant brain ... it was a conversation with him which gave me the idea which played a large part in winning the Battle of Alamein."

Williams had noted that Rommel deployed his infantry and parachute troops between and sometimes behind Italian troops, a tactic known as "corsetting".

"Bill Williams's idea," Montgomery said, "was that if we could separate the two we would be very well placed as we could smash through a purely Italian front without any great difficulty." This strategy, known as "crumbling", involved luring the Germans out of their original positions.

Most of Montgomery's seemingly miraculous insight into Rommel's intentions came to him from information supplied by Williams and not, as he used to claim, from studying the photograph of Rommel which he kept in his caravan.

But Montgomery was unstinting in his praise for Williams: "He was the main. source of inspiration; intellectually he was far superior to myself or anyone on my staff but he never gave that impression. He saw the enemy picture whole and true; he could sift a mass of detailed information and deduce the right answer.

"As time went on he got to know how I worked; he would tell me in 10 minutes exactly what I wanted to know, leaving out what he knew I did not want to know."

Montgomery believed that once a commander and his intelligence chief reached that degree of co-operation they should not be parted - "and that is why he went right through to Berlin with me. He was 'accepted' in and trusted right through the 8th Army.

"In this respect he was possibly helped by the fact that he wore a KDG [King's Dragoon Guards insignia] in his cap and not that of the intelligence Corps. The best officers in the Intelligence Branch of the staff were civilians ... and Bill Williams stood out supreme among them all."

When writing these tributes in his memoirs (published in 1958) Montgomery was unable to disclose the fact that Williams's genius included the ability to analyse and assess the products of the top-secret Ultra operation, in which intercepted enemy wireless traffic was translated and interpreted by a huge team of analysts at Bletchley Park.

Although Williams had no illusions about Montgomery's character, and what he referred to as his "peacock vanity", he liked him, and they became close friends. Yet Williams did allow that Montgomery was so bitterly disappointed. when he lost supreme command in Europe to Eisenhower that he was thereafter determined to show the Americans that he was the better man; and that this led to such rash moves as the failure to clear the Scheldt Estuary before embarking on Operation Market Garden.

Nor did Williams fail to record "Monty's" little quirks - such as appropriating captured stationery and using it, complete with foreign language headings, for his correspondence with the War Office.

As well as dealing with the demanding and temperamental Montgomery, Williams was required to be a morale builder, detective and first-class actor - during the desert war the quality of the intelligence from Ultra was so good that he was often questioned about its source and had to give plausible replies to officers superior in rank.

"I tried to make him a general," said Montgomery, "but he didn't want it, didn't want it."

A clergyman's son, Edgar Trevor Williams was born on Nov 29 1912 and educated at Tettenhall College, Staffs, King Edward's School, Sheffield, and Merton College, Oxford, where he was a Postmaster (scholar) and took a First in History. After a lectureship at Liverpool University he returned to Merton in 1937 as a junior research fellow.

In June 1939 he was commissioned in the Supplementary Reserve of Officers and later joined the 1st King's Dragoon Guards, serving with armoured cars in the Western Desert in 1941. In February 1942 he saw action against Rommel's troops in Cyrenaica.

When de Guingand was appointed Auchinleck's director of Military Intelligence he promptly selected a junior captain, for his Intelligence staff. De Guingand subsequently wrote that Williams "hated soldiering". This was not true; he had a great affection for the Army but did not wish to become a regular soldier.

That August, Montgomery inherited both de Guingand and Williams when he assumed command of 8th Army. Williams then served through North Africa, Sicily, Italy and Europe, eventually becoming Chief Intelligence Officer in 21st Army Group, which invaded France and continued to Berlin.

Among Williams's coups was the discovery that the Germans were trying (rather unsuccessfully) to produce a version of the British Long Range Desert Group with their Brandeburgers.

In 1945 Williams was elected a Fellow of Balliol and from 1946 to 1947 he worked for the United Nations Security Council Secretariat in New York. Although his post as director of the division of enforcement measures was highly paid, he resigned after a year, saying it was "a complete waste of time" and went back to academic work. The cause of his frustration was that he was working under a Russian who refused to give him any responsibility because he was a former British Intelligence officer.

In 1952 Williams became warden of Rhodes House, and seven years later added to his responsibilities the position of secretary to the Rhodes Trustees. He oversaw the selection procedures for scholars, guided the development of the scholarship scheme (including the admission of women in 1977), and each year attended to the well-being of nearly 200 scholars.

Williams was a skilled mentor to new scholars, who came to appreciate his pithy, elliptical and above all candid comments on their progress, and he became much esteemed by the wider community of former scholars. They saw him, in the words of one, as a "father-figure, fixer, and friend".

Rhodes House was also a centre for Commonwealth studies. Williams continued his interest in colonial history through participation in research seminars. In 1959 he was a member of the Devlin Commission on Nyasaland, and in 1980 an observer at the Rhodesian elections.

His 28 years as warden were matched by service to the university for almost as long, as a member of the Hebdomadal Council, a Curator of the Chest (or finance committee), and latterly as Pro-Vice-Chancellor.

He was a brisk and stylish chairman, given to shrewd, donnish assessments of individuals and policies, and rather avuncular in manner: he was liked and trusted. Business was usually salted with humour: he coined the word "montificate". After five years on Mongomery's staff, he said, "I could montificate with anyone."

His services were much in demand outside Oxford. He served as a Radcliffe Trustee and as a member of the Nuffield Provincial Hospitals Trust, and was a far-sighted chairman of the Academic Advisory Board which planned Warwick University. A keen cricketer, he served for many years as senior treasurer (and in 1966 to 1968 as president) of the Oxford University Cricket Club.

From 1949 to 1980 Williams was joint editor (with Helen Palmer and later with Christine Nicholls) of the decennial supplements to the Dictionary of National Biography.

It was unusual that in the course of such a long and distinguished academic career he should not have produced a single book of his own. Even his contributions to the DNB (which included finely honed essays on Churchill and Montgomery) are few in number. This is regrettable, for he was witty in print, and an incisive stylist.

He was thrice mentioned in despatches during the war; awarded the DSO in 1943; appointed CBE in 1944, CB in 1946, and a Deputy Lieutenant for Oxfordshire in 1964. He was knighted in 1973.

Williams married first, in 1938, Monica Robertson; they had a daughter. He married secondly, in 1946, Gillian, younger daughter of Maj-Gen M D Gambier-Parry; they had a son and a daughter.

[Daily Telegraph]