DENIS WRIGHT was one of the most effective ambassadors that Britain sent to Iran since Elizabeth I ruled over England. The British relationship with that important country has often proved to be complex. Wright first went there in 1954 as the chargé d’affaires chosen to reopen the embassy after the overthrow of Muhammad Mosaddeq, who had nationalised the Anglo-Iranian Oil Company and broken off relations with Britain. He successfully resumed relations with the Iranian Government and in 1955, when Sir Roger Stew had arrived to head the mission, he returned to the Foreign Office as an assistant under-secretary dealing with Middle East affairs.

In 1963 Wright went back to Tehran, this time as ambassador, and remained there until his retirement in 1971. He was able to gain the confidence of the Shah and that of his chief minister, Asadullah Alam (with whom he used to go on early morning rides). His most notable diplomatic achievement may have been to encourage the Iranians to forgo their claim to sovereignty over Bahrain, where they had exercised control from 1602 to 1783. This contributed to stability in the Gulf when Britain was withdrawing forces from east of Suez.

For an ambassador to remain at the same post for as long as eight years is almost unprecedented. The story goes that the Foreign Secretary twice had in mind to transfer Wright to a larger capital. But, on the first occasion, he was met by protests from the Western oil companies operating in Iran and, on the second, by objections from the Shah. For their part, the Wrights themselves preferred to stay in Iran where, having worked hard to learn Farsi, they travelled widely, at times on horseback or on foot, and made a host of friends at every level. For relaxation from the summer heat they loved to camp in the Lar valley at 8,000ft. There he fished while Iona, his wife, painted.

Wright was blessed with a quick mind, a sturdy frame, a generous nature and vigorous energy. His hair long retained its youthful colour and such was his vitality that his many friends half believed he might go on for ever. One of his godsons recently saw him, aged 93, striding along a platform at Basingstoke station, carrying a suitcase in each hand and with his wife in tow.

After more than 30 years in the Foreign (later Diplomatic) Service, Wright retired at the statutory age of 60. He then was able to pack several further careers into a long and active retirement. For a decade he was a director of such companies as Shell, Mitchell Cotts and the Standard Chartered Bank. He then appeared as a lecturer at universities in the United States. Finally, he emerged as an authority on Iranian studies and author of books and articles on Iranian history. He was president of the British Institute of Persian Studies, 1978-87, and held honorary fellowships at St Edmund Hall and St Antony’s College at Oxford.

Throughout these years of retirement Denis and Iona, whom he married in 1939, made a comfortable home in Buckinghamshire. There, in a house and garden adorned with Persian carpets, they entertained generously a stream of friends and visitors, both British and Iranian. Despite his success and the honours bestowed on him, Wright remained a modest man who often attributed his achievements to the help of others. He decreed that he wished to have no memorial service when he died but rather a simple funeral service in the parish church, St Mary’s. It was packed for the event.

Wright also had a sharp sense of what was right and wrong. Once, when he was on a lecture tour in the United States, he stayed in a southern city with the British consul, who had previously been on his staff in Tehran. Spotting a book on Iran in the bookcase, he took it down and found “British Embassy, Tehran” stamped on the flyleaf. “You must send this back immediately,” he told his host; and back it went.

Denis Arthur Hepworth Wright was born in 1911, the son of a superintendent of public works in Hong Kong. He was educated at Brentwood School, Essex, and at St Edmund Hall, Oxford. There he joined the Labour Club, where the prettiest girls were said to congregate. One of them was Iona Craig, a fellow undergraduate. On graduation in 1935, he joined Gallaher and Co, the tobacco company, as an assistant advertising manager.

In 1939 Wright was in Romania, where the British Embassy enlisted him as a vice-consul for economic warfare work at the British Consulate in the port of Constanta. Iona then travelled from England by train to marry him there. Years later, she was to write an engaging memoir of their experiences under the title of Black Sea Bride (1991).

In 1941 Wright was transferred to Trebizond on the northeast coast of Turkey as vice-consul in charge of the British Consulate, his first independent post. In 1943 he was promoted to be acting consul at the consulate at Mersin on the Mediterranean coast. During the first postwar decade Wright was appointed to a series of economic posts — as first secretary (commercial) in Belgrade, as trade consul in chicago and as head of the economic relations department in the Foreign Office. In each appointment he enhanced his reputation.

Then came the turning point of his life, when he was chosen, in 1954, to lead the team sent to Tehran to re-open the embassy and to resume relations with Iran. In diplomatic life, such opportunities seldom arise. Forty years later, Wright contributed a memoir to Travellers’ Tales (1999), a book written by members of the Travellers’ Club in London, which tells the story. His team were some of the brightest and best the Foreign Office could muster. The Iranians declined to accept three out of the four who had previously served in Iran. The fourth, who was able to travel, was John Fearnley. Others included Charles Wiggin, later Ambassador to Spain, and Dick Franks, a future head of MI6.

In 1959, Wright was given his first embassy — at Addis Ababa. There he displayed a cool head by warning Emperor Haile Selassie, who was on a visit to Latin America, that a military coup had occurred. The Emperor was able to return in time to put down the uprising. Thereafter, he recognised his debt to Wright, took him into his confidence and sometimes even lent him his mules. The best way to travel was by mule train and the finest mules were in the imperial stables.

When the Iranian revolution occurred and the Shah abdicated in 1979, Wright had been retired for almost a decade. But the Foreign Office persuaded him to take on the unpleasant task of flying to Bermuda to inform the Shah that the British Government could not grant him asylum. He and the Shah both understood that relations between states are by nature based on self-interest.

Wright’s many books include The English among the Persians (1977) and The Persians among the English (1985). To honour Wright’s achievements, the Royal Society for Asian Affairs awarded him the Sir Percy Sykes Memorial Medal in 1990; and in 2003 the Iran Society, of which he had been both a chairman and president, published his collected essays Britain and Iran, 1790-1980. He is survived by his wife.

Sir Denis Wright, GCMG, Ambassador to Iran, 1963-71, was born on March 23, 1911. He died on May 18, 2005, aged 94.