Clash of the press titans
The actions of Rupert Murdoch's newspaper group have drawn the wrath of Westminster, but this is not the first time that politicians have done battle with mighty press barons.
When the Times flexed its considerable muscle at the ruling classes of the mid-19th century, it was enough to turn the politicians' faces the shade of a modern-day red-top.
Known as the Thunderer, it was arguably the most influential daily in the world, of which Abraham Lincoln said: "I don't know of anything which has more power, except perhaps the Mississippi."
When press titans have tried to push their own political agenda, power struggles have occasionally erupted, sometimes in spectacular fashion.
Stanley Baldwin v Lords Rothermere and Beaverbrook
Historian Dr Piers Brendon has described UK press magnates as "mad, bad, dangerous-to-know beasts in the newspaper jungle who did what they wanted". He may well have had Lords Rothermere and Beaverbrook in mind.
The respective owners of the Daily Mail and Daily Express arguably held a tighter grip on the news agenda than modern-day magnates. These tycoons were free from the diluting influence of TV, radio and other media.
The Express covered the entire spectrum of classes and in the 1930s was the first paper to have a circulation of two million - a huge total at the time.
In 1930 the barons almost ousted former Prime Minister Stanley Baldwin as leader of the Conservative party by running two separate campaigns against him on the issue of empire free trade.
Baldwin favoured protectionism whilst the two Lords wanted the British Empire to become a free trade bloc, setting them on a political collision course.
When Beaverbrook formed the Empire Free Trade Crusade, a campaigning political party, and started running by-election candidates alongside Rothermere, Baldwin snapped.
On 17 March 1931 he delivered his now famous speech at the Queens Hall in London, some of which was supplied by his cousin Rudyard Kipling.
"Their newspapers are not newspapers in the ordinary acceptance of the term, they are engines of propaganda for the constantly changing policies, desires, personal wishes, personal likes and personal dislikes of two men," he thundered.
"What the proprietorship of these papers is aiming at is power, but power without responsibility, the prerogative of the harlot throughout the ages."
Dr Brendon, author of The Life and Death of the Press Baron, says the use of Kipling's phrase "harlot" was genuinely shocking at the time, and enough to shut the barons up.
He says Beaverbrook had openly admitted running his newspapers to promote his own political agenda, and was unapologetic.
A year earlier, Rothermere refused to support Baldwin unless he provided him with the names of at least eight out of 10 of his future cabinet should he be elected.
Baldwin replied: "A more preposterous and insolent demand was never made on a leader of any political party. I repudiate it with contempt and I will fight that attempt at domination to the end."
Harold Wilson v Cecil King
Cecil King is notorious for trying to bring down the government of Harold Wilson with a front page.
He was chairman of the Daily Mirror's parent group during the 1960s when the paper sold over five million copies. By 1968 he had become disillusioned with Wilson's government and moved to topple the prime minister.
On 10 May, he went over the head of Mirror editor Hugh Cudlipp and ran a front page with the headline "Enough is enough."
Geoffrey Goodman, a former assistant editor of the Daily Mirror, described it in the Guardian as a "sensational piece written and signed by King demanding Wilson's dismissal by his own government and removal from 10 Downing Street".
But the move backfired. When King called a meeting of those he hoped to recruit for his national government, they reacted to his plan by calling him a traitor and storming out.
And the Mirror Group board responded by sacking King and replacing him with Cudlipp. "It was a mad idea," says Roy Greenslade, who wrote about the episode in his book Press Gang.
The genesis of King's anger with Wilson was a sense of injustice, Greenslade believes. He had wanted a cabinet post when Wilson's government was elected in 1964.
He also viewed Wilson's policies as too left wing. In the end, his behaviour was continuing a venerable family tradition. King's mother was the sister of Lord Northcliffe.
"There was something in the genes," Greenslade says. "It all goes back to Northcliffe."
Herbert Asquith v Lord Northcliffe
"In terms of the press baronetcy, Northcliffe is number one," says Roy Greenslade.
Born Alfred Harmsworth in Ireland, he was a pioneer of tabloid newspapers. With younger brother Harold - later the first Lord Rothermere - he launched the mass market Daily Mail and later bought the Times.
The former became the highest selling newspaper in the land, while the latter gave him a direct line to the British establishment.
Before World War I his papers demanded a strongly anti-German line, prompting the Daily Star to declare: "Next to the Kaiser, Lord Northcliffe has done more than any living man to bring about the war".
By this point, his newspapers accounted for half of those sold in London. In 1915 the Times seriously undermined PM Herbert Asquith, paving the way for Northcliffe favourite David Lloyd George to replace him in Downing Street the following year.
Lloyd George responded by offering him a seat in cabinet. Northcliffe declined and instead took up the post of director of propaganda.
"He had the masses with the Daily Mail and the ruling classes with the Times," Greenslade says.
For a time the vast circulation of his papers gave him unrivalled power.
For sheer political influence, he was surpassed by Lord Beaverbrook, Greenslade believes. But Northcliffe remains a towering figure in the history of newspaper proprietors.
He is credited with the line: "News is what somebody somewhere wants to suppress, everything else is advertising". (A variant of this is also attributed to US newspaper baron William Randolph Hearst.)
The cartoonist Max Beerbohm portrayed him struggling to restrain his tabloid instincts, with the line: "'Help! Again I feel the demons of sensationalism rising within me! Hold me fast!'" His legacy lives on today in the form of Northcliffe House in Kensington, home to the Daily Mail.
Clement Attlee v Lord Beaverbrook
In the austere years following World War II, Labour Prime Minister Clement Attlee used a different method to tackle a hostile press - flatly ignoring them.
It was a tactic that proved highly successful, according to Dr Brendon, as it allowed him to focus on policies such as establishing the welfare state and nationalising major industries.
By now, Express owner Lord Beaverbrook - the first baron of Fleet Street - presided over the world's largest selling newspaper with a circulation approaching four million.
He had a reputation to be able to make or break almost anyone.
Historian and author Richard Heller says Attlee was so removed from the media that he had to be persuaded by his press secretary, Francis Williams, to install a tape machine at Number 10 to monitor breaking news.
Williams only sold the idea to cricket fanatic Attlee on the basis that it would give him access to the latest scores, Heller says.
One day when Attlee was checking the scores he was horrified to notice that the machine was also clattering out political news, the historian adds.
"Francis," Attlee said, "My cricket machine's gone wrong. It's putting out stuff about the government."
Williams replied: "I know, prime minister, I put it there."