The unwritten law in the old Fleet Street was that the proprietors may have rivalries and disagreements but they don’t make war on each other.

That concordat has broken down in the most dramatic fashion with the liberal Guardian opening its guns on Rupert Murdoch’s conservative UK newspaper empire.

With the completion of this year’s painfully predictable Wimbledon, the reading public has become enthralled by The Guardian’s accusations that “The Dirty Digger’s” London lieutenants are up to the armpits in a celebrities’ phone tapping scandal.

On the face of it, the contest is heavily weighted in Murdoch’s favor because he occupies leading positions in the gutter press — the Sun and the News of the World — and the pavement press, The Times and The Sunday Times.

But The Guardian has the high moral ground, the criminal law, many MPs, the BBC, the intelligentsia and the opinion-makers on its side in this gripping stoush.

It started last week when The Guardian devoted two editions to exposing the way Murdoch’s News of the World used private detectives to hack into the phones of celebrities to publish “scoops” about their private lives.

The results of the year-long investigation produced 25 separate articles in Thursday’s paper and seven pages more on Friday. The inquiry has been masterminded by award-winning journalist Nick Davies, the author of Flat Earth News who was one of the acclaimed guests at the Melbourne Writers’ Festival last August.

In fact, The Guardian has published only a fraction of what its reporters have dug up. Under the wily hand of editor Alan Rusbridger the paper has obviously decided to roast News International slowly and build public opinion.

In 2007, Clive Goodman, the News of the World’s royal correspondent, and private security agent Glenn Mulcaire were jailed for illegally obtaining information after being caught redhanded trying to access the phones of members of the royal household.

As a result, News of the World editor Andy Coulson fell on his sword and went off to become communications director to the Tory leader David Cameron, the man most likely to become Britain’s next Prime Minister.

Although a parliamentary committee was told Goodman was “a rotten apple”, everyone in the media believes he was “a patsy”.

So far The Guardian has established an unassailable case that the News of the World, and probably its sister paper the Sun, have been engaged in systematic criminal behavior to obtain confidential information to fuel its celebrity-driven news pages.

However, the establishment institutions which are supposed to monitor these issues — Scotland Yard, the Director of Public Prosecutions and the Press Complaints Commission — seem to have given only perfunctory consideration to the media group’s misbehavior.

As Private Eye co-founder and editor of The Oldie Richard Ingrams said, “It is perfectly clear that the News of the World has broken the law and equally clear that the police don’t want to do anything about it.”

However, a House of Commons all-party committee is now taking a keen interest in The Guardian allegations and whether there has been a cover-up. One matter which is exciting MPs is whether News International journalists have been paying police officers significant sums of money for information on celebrities — their unlisted phone numbers, tracing car registration numbers and accessing criminal records.

Around London nightclubs, restaurants and bars, the celebrities who have fallen victim to snoops from News International papers are hoping that their torment will be avenged and that other editorial executives will follow Clive Goodman into the slammer.

They are also calling their lawyers and asking the price of legal action to extract damages following News International’s admission that it paid more than $1.4 million to settle a law suit brought by Gordon Taylor, CEO of the Professional Footballers’ Association.

Dumbing down newspapers — and editorial staff — may yet come at a very high price for News shareholders.