David Astor, who died on December 7th aged 89, was one of the most influential newspaper editors of the 20th century, through the Observer, which he edited for nearly 30 years from 1948-'75. But his influence extended through a discreet and impenetrable network of charities, lobbies and close friendships.
He was an idealist who learned how to turn ideas into execution, with a combination of sensitivity and persistence. He appeared diffident, but was very determined. He had natural charm, but remained shy and uneasy with small talk.
His contradictions were forged by his family background. He was devoted to his father, Waldorf, one of the richest men in Britain, with a strong social conscience. As a child at his parents' mansions - at Cliveden, in Buckinghamshire, and in St James's Square, London - he had a nursery view of world politicians and statesmen. But he was soon at odds with his mother Nancy, the first woman MP to take her seat, who tried to impose her conservative views and belief in Christian Science on her family.
At Eton, his tensions with his mother induced a breakdown and, later, he left Balliol College, Oxford, without taking a degree.
He took many years to find his metier: he worked briefly at Lazard's bank, then at the Yorkshire Post and, in Yorkshire, putting on pantomimes. But he was increasingly preoccupied by the coming world crisis, influenced by his friend Adam Von Trott, the young German idealist who sought to avert the Nazi catastrophe and was hanged in 1944 for his part in the plot against Hitler.
In 1940, while he was serving in the Royal Marines, his father reached deadlock with J.L. Garvin, the autocratic editor of the Observer, which Waldorf owned. Garvin was finally dismissed in 1941, to be followed by stop-gap editors, while David Astor began contributing to the paper during his lunch hours. After the war, he took increasing responsibility until, in 1948, he was appointed editor.
He had little respect for the conventions of journalism, but he had a flair for editing and nursing talent; he saw himself as a kind of chef, mixing dishes and ingredients. He hired intellectual friends - including George Orwell, Arthur Koestler, Isaac Deutscher, Sebastian Haffner - and turned them into journalists.
He always looked for unorthodox thinkers. His friend John Strachey, the former war minister, once told him that the civil servants with whom he disagreed were always described as "sound", which made Strachey look for people who were unsound. David Astor was equally suspicious of "sound" views.
He was determined to maintain the Observer's independence. He never really trusted the Conservatives, but rejected socialist dogma and could be quite fiercely anti-communist.
He was one of the first to realise the dangers of the apartheid government in South Africa in 1948, which he saw as perpetuating Nazi racialism. He befriended the young Nelson Mandela, when he visited London in 1962, and sent him law books in jail. He later became a trusted ally of Mandela's colleague Oliver Tambo - for whom, in 1986, he set up a project to train young ANC people for government.
The Observer in the 1950s was a newspaper like no other: eccentric, amateurish, indulgent, but with a distinction and intellectual courage that attracted readers with a passionate loyalty. David Astor presided, with amused tolerance, over neurotic contributors and could get the best out of a wide range of writers, including Philip Toynbee, Edward Crankshaw, Ken Tynan, Michael Davie, Katharine Whitehorn, Patrick O'Donovan, Michael Frayn, Neal Ascherson and John Gale.
He had an uncanny ability to understand other people's problems. He had been psychoanalysed by Anna Freud after his first marriage, to Melanie Hauser, in 1945; and it was not until he married Bridget Wreford, in 1952, that he had a totally secure home life.
He was bored by commercial questions, economics and advertisers. Yet the Observer steadily crept up on the Sunday Times and, by 1956, was about to overtake it.
Then came Sir Anthony Eden's invasion of Suez, which David Astor saw as a crazy blunder, and which he attacked in a passionate editorial: "We had not realised that our government was capable of such folly and crookedness." David Astor saw it as his Agincourt. It appalled loyal conservative readers; Jewish companies withdrew their advertising, and three of the seven trustees resigned.
The paper found new readers, as the Manchester Guardian did, but the Observer never recovered its commercial momentum.
He accepted more popular consumer features, but never compromised over the intellectual core of the paper; and he boldly pursued his central interests - whether it was the search for reconciliation in the Middle East, the defence of minorities or the opposition to apartheid.
In 1975, he retired as editor, while remaining a director. The paper still lost money and, after looking at other bidders - including James Goldsmith and Rupert Murdoch - he welcomed a surprising rescuer in the American oil tycoon Robert Anderson, who later brought in Conor Cruise O'Brien as editor-in-chief.
But, in 1981, Anderson tired of the Observer's losses - and its support for Labour - and surreptitiously sold it to his friend "Tiny" Rowland, who wanted it to support his African commercial interests.
David Astor was horrified to see his life work thus exploited, and tried in vain to stop the deal through the Monopolies Commission. As the paper became more obviously influenced by Rowland's commercial battles, his protests were vindicated.
But David Astor was almost as active without the Observer.
He had initiated an extraordinary range of trusts, charities and pressure groups, and was a founder member, in 1972, of the British Irish Association. He served as its chairman from 1976 until 1990.
Extraordinarily modest, he played an important behind-the-scenes role encouraging politicians toward the search for settlement.
He could never resist trying to change the world, he explained apologetically. Many of his causes - including the battle against apartheid - were eventually won. He was delighted, in 1993, to see the Observer acquired by the Guardian.
He is survived by his wife Bridget and their children, and by one child from his first marriage.
Francis David Langhorne Astor: born 1912; died, December 2001