David Cameron has paid tribute to "Fleet Street legend" Lord Rees-Mogg, who has died after a short illness aged 84.
As William Rees-Mogg, he was editor of The Times from 1967 to 1981 and went on to become an influential columnist.
His son, Conservative MP Jacob Rees-Mogg, said the peer had only discovered recently that he had inoperable oesophageal cancer.
"It has been a mercifully short illness. He died very peacefully and a member of his family was with him. He was very prepared for it," Jacob Rees-Mogg told The Times.
Lord Rees-Mogg was at the helm of The Times during Rupert Murdoch's 1981 takeover.
During his editorship, he was credited with making the reporting more investigative and the paper's opinions more challenging.
After his tenure as editor, Lord Rees-Mogg was a columnist whose opinions were highly influential in Tory circles, particularly during the Thatcher and Major governments. He was also vice chairman of the BBC's board of governors (1981-86) and chairman of the Arts Council (1982-89).
The Prime Minister led tributes.
He said: "William Rees-Mogg is rightly a Fleet Street legend - editing The Times through a tumultuous period with flair and integrity.
"I always found him full of wisdom and good advice - particularly when I first became leader of the Opposition.
"My thoughts are with his wife and five children at this sad time."
BBC Trust chairman Lord Patten said: "William Rees-Mogg was a great journalist and editor, and a distinguished public servant, for example at the Arts Council and BBC.
"My family knew him as a kind and good man, generous, spirited, warm, witty, and the much-loved father of a close and talented family.
"Everyone who knew him will miss him deeply."
Lord Rees-Mogg received a life peerage in 1988 and sat as a cross-bencher.
He went on to challenge the legality of John Major's ratification of the Maastricht Treaty. But three High Court judges rejected his contention.
Press Association’s Chris Moncrieff writes:
Lord Rees-Mogg, one-time editor of The Times and chairman of the Broadcasting Standards Council, was a man of trenchant views who once famously but unsuccessfully challenged the legality of John Major's ratification of the Maastricht Treaty.
This action was described by one critic at the time as being in character: "showy, mischievous, slightly absurd, but with a dash of plausibility".
His regular articles in The Times, in the latter part of his life, sometimes strayed into the realms of pontification. But they always carried weight and authority and were often quoted in the House of Commons.
In 1964 he wrote a famous article headed "A Captain's Innings" in the Sunday Times in which he called for Alec Douglas-Home to resign as Prime Minister, which he did shortly afterwards.
This was regarded as one of the most influential pieces of post-war British political journalism. But Douglas-Home rather spoiled that boast when he said later that he had already decided to quit before the piece appeared - and anyway, he lost the election.
Later Rees-Mogg, in an article in The Times which other newspapers turned into front-page news, described John Major, the then Prime Minister as "over-promoted, unfit to govern and lacking self-confidence. His ideal level of political competence would be Deputy Chief Whip or something of that standing."
This was immediately denounced by Sir Norman Fowler, then the Tory Party chairman, as "the authentic voice of the Patrician Tendency - pure snobbery".
William Rees-Mogg was born on July 14, 1928. He was educated at Charterhouse, where he was head of school and respected for his stock-market dabbling.
He then went to Balliol College, Oxford, where he was Brackenbury Scholar and President of the Union. In 1952, he joined the Financial Times where he worked until 1960, part of the time as chief leader writer and also assistant editor.
In 1960, he joined the Sunday Times where he was successively City Editor, Political and Economic Editor and Deputy Editor, before becoming editor of The Times in 1967, a post he held until 1981. He was only 52 when he retired to a life peerage (which came in 1988) and membership of several worthy bodies - plus, of course his regular and inimitable column-writing.
During his editorship of The Times, he stubbornly defended Richard Nixon against all the Watergate evidence filed by his Washington staff.
But he was a radical editor, making the reporting on The Times more investigative and its opinions more challenging. He was in the vanguard of the Tory modernisers in the Edward Heath era.
There was no questioning the paper's authority under his editorship, but his tenure of office ended in tears.
The staff had formed a group called Journalists of the Times which opposed Rupert Murdoch's 1981 takeover.
Possibly ill-advisedly, Rees-Mogg assumed leadership of the group and unsuccessfully sought an alternative buyer which, in his view, would have guaranteed the paper's editorial independence. Later, he threw his high reputation behind Murdoch, and the staff felt betrayed.
In his maiden speech in the House of Lords in 1989 he advanced an eccentric constitutional theory that claimed power for the Upper House to block Commons legislation on the machinery of justice.
In July, 1993, three High Court judges unanimously rejected Rees-Mogg's contention that the Major Government could not lawfully ratify the Maastricht Treaty because Parliament had not approved the social protocol.
They ordered Rees-Mogg to pay the costs, estimated at hundreds of thousands of pounds.
When he was chairman of the Broadcasting Standards Council, Rees-Mogg put Coronation Street through the hoops. He said it was a relic of the Macmillan era and bore little resemblance to modern society.
He said the famous soap did not have enough ethnic minorities in it.
Elsewhere, Rees-Mogg held a number of appointments: He was High Sheriff of Somerset in 1978, chairman and proprietor of Pickering and Chatto Ltd, booksellers and publishers, a director of General Electric, and chairman of the Arts Council of Great Britain, 1982 to 1989.
And although he sat in the House of Lords as a cross-bencher, he twice unsuccessfully fought a parliamentary seat as a Conservative candidate: Chester-le-Street in 1956 (by-election) and in 1959 (general election).