And in search of sexual and political scandal they hacked into the phones of thousands of others; the London police say they have a list of 4,000 people who might have suffered their attentions.

Discovery of these serious crimes has brought forward a crisis that was already culminating. News International’s bid to take control of the television company British Sky Broadcasting, or BSkyB, was, in the opinion of many, a step too far, given that, even before the hacking revelations, its influence on politics and public conversation had become deeply corrosive.

The Murdoch media have influenced every election in Britain since the Thatcher era. Both major political parties have courted Mr. Murdoch in hope of his support, and when he gave it, they flourished at the polls. In return, he was allowed to take control of increasing stretches of the media landscape, meanwhile dissuading government from regulation that would hamper his operations. He already owns 39 percent of BSkyB; his reason for wishing to own it all is, as he has publicly indicated, to make it more like its American counterpart, Fox News.

Mr. Murdoch’s influence over successive governments has long been a concern. His hostile attitude toward the European Union and his ingratiating attitude toward China, to name but two examples, have influenced politicians eager to please him. That the former News of the World editor, Andy Coulson, was, until the hacking scandal broke, Prime Minister David Cameron’s trusted director of communications, is only the latest instance of this unseemly influence. Mr. Coulson is now under arrest for being part of the hacking crimes. Significantly, when the scandal emerged in 2005 under the Labor government, the police did little to pursue it; only now, under public pressure, have they begun to alert hacking victims to what happened back then.

Tabloid practices have always had a corrupting effect on the public conversation, but they reached new depths under the editorship of The News of the World by Mr. Murdoch’s much-favored deputy, Rebekah Brooks. The cynicism of tabloid technique is well understood: Splash a rumor as news on the front page, then print a one-line retraction on an inside page two weeks later. By then, the victim has been thoroughly damaged, with other papers, and the graffiti wall of blogs and Twitter, transmitting the allegations globally.