Sir Harold Beeley, who has died aged 92, was for many people the personification of British efforts in the postwar period to develop a new and healthy relationship with the Arab world, a cause in which he persevered throughout his long life.
Born in Manchester and educated at Highgate school, he began as an academic historian, one of that distinguished number of Oxford dons - he was a lecturer from 1935-38 at Queen's College, where he had been an undergraduate - whose experience of government work during the second world war led them into public service careers.
His time in the Foreign Office research department preceded secondment to the secretariat of the 1945 San Francisco conference, and the preparatory commission of the United Nations. With the American diplomat Ralph Bunche, he played an important part in devising the UN trusteeship system for the so-called dependent territories, perhaps Bunche's most enduring legacy.
Beeley was appointed secretary of the Anglo-American inquiry on Palestine in 1946; he joined the Foreign Service in the same year, and almost his entire career thereafter was divided between the UN and the Middle East.
In his very first job, as desk officer for Palestine in 1947-48, he established a relationship with the then foreign secretary, Ernest Bevin, and, despite his junior rank, became Bevin's principal adviser during the critical events surrounding Britain's withdrawal from Palestine and the creation of the state of Israel.
Although his sympathies were - and remained - with the Palestinians, Beeley did his utmost to reconcile Britain's conflicting obligations to both sides. This did not prevent his being cast, alongside Bevin in Israeli legend, as a malevolent midwife at the birth of the state.
After a quiet spell in Baghdad in the early 1950s, when the ill-starred Baghdad Pact - let alone the 1958 Iraq revolution - were barely clouds on the horizon, Beeley was back at the heart of things in the Washington embassy.
There, he developed the close working relationship with the State Department that endured well beyond the decline of Britain's influence in the Middle East. He was then appointed ambassador to Saudi Arabia, to try to repair the crisis in relations caused by Britain's expulsion of the Saudi occupying force from the Buraimi oasis in Oman.
Beeley had been in post for only a few months when he was called back to the Foreign Office in June 1956, to be assistant under-secretary for Middle East affairs; he thus saw the Suez affair from the start. He played a full part in diplomatic efforts to resolve the crisis, and chaired the abortive Suez Canal Users' Association.
But when the Israeli-Franco-British plot to use force was hatched, Beeley - like everyone else in the Foreign Office, apart from its most senior official and a private secretary - was kept in the dark, and the most fateful initiative in British foreign policy since Munich proceeded in deliberate disregard of expert advice.
Although the politicians were discredited, the policy of hostility toward Egypt's President Nasser was not, and Beeley was obliged to remain a passive, if sceptical, accomplice in the new Anglo-American Eisenhower doctrine, which sought to build a conservative Arab coalition around Saudi Arabia, and which reacted to the setback of the Iraq revolution with the empty gesture of dispatching troops to Lebanon and Jordan.
Beeley found a more congenial role in New York, where he was again plunged into crisis diplomacy through the Beeley-Murphy mission of 1958. Named after Bob Murphy, General Eisenhower's wartime political adviser in North Africa, and by then deputy US secretary of state, this attempted, with limited success, to defuse the effects of French cross-border bombing raids into Tunisia.
During the mission, Beeley established a particular rapport with the UN secretary general, Dag Hammarskjöld, who had a high respect for his intellect and judgment, and was closely involved in both the UN peacekeeping operation in the Congo and in Hammarskjöld's painstaking - and posthumously successful - negotiations to resolve the Buraimi dispute.
When diplomatic relations with Egypt were eventually resumed in 1961, Beeley was the natural choice to be ambassador in Cairo. The political climate was, however, unpropitious, with British ministers suspicious of the Egyptian role in the Congo and, later, in the Yemen, where Egypt's intervention in support of the republican coup was seen as a threat to the British position in Aden.
Beeley therefore began by concentrating on practical bilateral issues and, within a couple of years, had cleared up most of the debris of the Suez affair, including a settlement of the compensation claims of British nationals expelled from Egypt, and the return of the British Council to the scene of its earliest beginnings overseas.
He gradually won the confidence of several of Nasser's key ministers, and built up a working relationship with Nasser himself. But the latter's deep-seated suspicion of Britain, plus the pervasive influence of the Soviet Union, made the task all but impossible and, not long after Beeley's departure, Nasser broke off relations again - on the bizarre pretext of the white Rhodesian unilateral declaration of independence.
Beeley had been transferred back to UN work, as representative to the UN conference on disarmament in Geneva, shortly before the Labour government came to power in 1964. Whether or not that transfer reflected a feeling among Conservative ministers that he had been too successful in cultivating Nasser, George Brown, who became Labour's foreign secretary in 1966, had no doubt that he was the man to rebuild relations with Egypt yet again, following the 1967 six-day war and UN resolution 242.
Beeley was delighted to return to Cairo, and became an influential figure on the political scene, the more so as no American ambassador appeared until after the 1973 war between Egypt and Israel. By the time he retired in 1969, he had laid the foundations for the rapprochement that developed under Presidents Sadat and Mubarak.
In retirement, Beeley lectured in history at Queen Mary College, London University, for six years, but he never published his own account of the events in which he had been involved. Now, more than half a century after the creation of Israel, his recollections would have been invaluable, but he had remarked some years ago that Alan Bullock's biography of Ernest Bevin provided ample vindication of his hero, and obviated any need for a contribution from him.
This reticence reflected the essential modesty of the man, and a genuine reluctance to seek the limelight. He preferred to work quietly and pragmatically to advance the Arab and Palestinian causes, serving for many years as vice-chairman of the periodical Middle East International, as chairman of the Egyptian-British Chamber of Commerce, and president of the Egypt Exploration Society.
He was also, from its inception, chairman of the World of Islam Festival Trust, and presided over its brilliant London exhibition of 1976, and numerous educational and other projects the trust has supported to promote the appreciation of Islamic culture in the west.
With his powerful intelligence and decisive judgment, their effect curiously enhanced by a permanently twitching eyebrow, Beeley could be a daunting presence on first acquaintance, but few ambassadors have been more popular with both their staffs and the foreign communities among whom they served.
For 40 years, he enjoyed a devoted relationship with his second wife, Karen, who died in 1999. He is survived by two daughters from his first marriage, to Millicent Chinn, and one from his second.