Rupert Murdoch's Sun newspaper prides itself on an aggressive reporting style that has delivered decades of sensational scoops and made it Britain's best-selling newspaper. But now it is the one being scrutinized, and it doesn't like it one bit.

Murdoch bought the Sun in 1969 and swiftly turned it into an irreverent muck-raking tabloid that came to be loved and loathed in equal measure by the nation it reported on. In a decade, circulation rose from 800,000 to 4 million.

The newspaper became so self-assured as to proclaim It's The Sun Wot Won It after backing the Conservative party to win Britain's 1992 general election, in just one of many front pages that have seared themselves into the national memory.

At times jingoistic, always merciless toward its targets, but unswervingly loyal to its proprietor, it established itself as a national institution that could not be ignored.

But now the hunter has become the hunted. The cheeky red top tabloid has been dragged into a damage limitation exercise launched by its owner, News International, after evidence of widespread phone-hacking led Murdoch to shut down the Sun's sister Sunday paper, the News of the World, last July.

Keen to put its house in order, the company set up a secretive committee of lawyers, police and executives who are holed up in soundproofed offices sifting through millions of Sun records for traces of wrongdoing.

As a result of the committee's work, 10 current and former Sun staff have been arrested over suspected corrupt payments since November and many of the Sun's current crop of journalists fear they are being sold out by Murdoch despite their loyalty.

The Sun journalists are extremely angry with Murdoch. He's shattered that special bond between him and them. They feel they're being scapegoated, Roy Greenslade, who was number three at the Sun during its heyday in the early 1980s, told Reuters.

The paper's woes mark an incongruous low point for a tabloid that is used to setting Britain's political agenda and one that can make or break the reputation of politicians and celebrities.

Few Britons who were old enough to vote in 1992 have forgotten the Sun's election-day front page on Labor Party leader Neil Kinnock, headlined If Kinnock wins today will the last person to leave Britain please turn out the lights.

While the Sun's claim to have clinched victory for the Conservatives was disputed, there is little doubt that years of abuse of Kinnock and other Labor politicians played a role in keeping the party out of power for 18 years.

PRIME MINISTERS PICK UP THE PHONE

A measure of its perceived power was the presence of then Prime Minister Gordon Brown and his successor-to-be, David Cameron, at the 2009 wedding of Rebekah Brooks, then the editor of the Sun.

Such clout, be it real or imagined, has seen politicians of all stripes pay court to Murdoch and the Sun for decades hoping to avoid a similar fate, although some influential figures in politics and media say they were misguided.

Conservative grandee Chris Patten last month told the Leveson inquiry into the ethics of the British press, triggered by the News of the World scandal, that politicians demeaned themselves by groveling to newspaper editors and owners.

There's plenty of evidence that in some cases, particularly News International newspapers, they back the party that's going to win an election. They give you what you don't need, he said.

When the editor of the Sun calls, prime ministers pick up the phone, Tom Watson, a lawmaker who has taken a leading role in parliament's efforts to hold News International to account since the phone-hacking scandal broke, told Reuters.

The Sun lampoons or vilifies those with whom it disagrees so fiercely that politicians are terrified of it, Watson said.

It revels in simplistic jingoism too, rudely attacking Britain's European partners, as in the famous Up Yours Delors front page of 1990, an insult to the then head of the European Commission, Frenchman Jacques Delors.

To the horror of Argentina, that jingoism was on display in 1982 when the British navy sunk the Argentine warship General Belgrano during the Falklands war. The Sun's stark banner headline: GOTCHA.

The paper has also angered women by continuing to serve up a daily diet of topless Page 3 girls. It revels in show business gossip in its Bizarre pages and loves titillating headlines such as last week's I slept with 1,000 men but I used to be a man myself.

The British public has embraced the tabloid. It sells 2.7 million copies a day, making it the country's best-selling paper, and is read by almost three times that number of people.

Long considered the jewel in the crown of Rupert Murdoch's British newspaper empire, News International, it is perhaps unsurprising then that the Sun has proclaimed itself The Greatest Paper In The World on a sign hanging in its newsroom in Wapping, east London.

The Sun is not a 'swamp' that needs draining, Trevor Kavanagh, former political editor of the paper, wrote this week, defending the payment of sources as standard procedure.

In an unprecedented step, Murdoch personally addressed staff grievances in London Friday to try to calm their concerns.

GLORY DAYS

Regardless of the outcome of the drama playing out at the Sun, some media insiders say its glory days are over.

The truth is the Sun has passed its sell-by date, said Greenslade, also the author of an authoritative history of the British press.

He cited steadily declining circulation figures, an aging readership not being replenished by young blood and the fact that the Sun's saucy content cannot compete with the Internet.

Greenslade also said the Sun had lost political clout, pointing to the 2010 general election when it strongly backed the Conservatives. They failed to win an outright majority and had to form a coalition with the Liberal Democrats.

Murdoch has no entree to Downing Street. That's over. Can he rebuild? No. He's persona non grata with all three party leaders now. He's damaged goods, Greenslade said.

Nevertheless, it takes a brave politician to stand up to the Sun, as former Labor minister Clare Short found when she criticized the paper's beloved Page 3 girls in 2003.

The Sun retaliated by publishing a doctored photograph of a bare-breasted Short, accusing her of being jealous, and parking a busload of Page 3 Girls outside her house.

Such cases provide fodder for Sun critics who say the paper's claim to act in the public interest is nonsense. But for the most part, those behind the Sun's success are unapologetic.

Kelvin MacKenzie, who edited the Sun from 1981 to 1994 and pushed up circulation to a peak of almost 4.3 million, told the Leveson inquiry that he didn't spend too much time pondering the ethics of how a story was gained.

MacKenzie was behind a front page story accusing fans of Liverpool football club of stealing from the dead and urinating on police during the 1989 Hillsborough disaster in which 96 people died in a stadium crush.

The paper later apologized for the unsubstantiated story, but sales of the Sun plummeted in Liverpool and never recovered.

MacKenzie's testimony also provided insights into the Sun's self-confidence in dealing with people in high places.

Asked about a phone conversation with John Major, then the Conservative prime minister, on how the Sun was going to cover Britain's humiliating exit from the European exchange rate mechanism in 1992, MacKenzie did not mince his words.

I said I've got a bucket of shit on my desk, prime minister, and I'm going to pour it all over you.

(Editing by Andrew Osborn)

Sun