Journalists at the News of the World used phone-hacking as a "perfectly rational but entirely illegal" way of checking stories, jurors heard today.
Prosecutor Andrew Edis QC told the Old Bailey that the tabloid would receive a tip-off about a story, and then use surveillance and phone-hacking to check whether it was true before confronting those involved.
He said the prosecution was not suggesting every story was obtained, or investigated, by phone-hacking, but that journalists used it as part of trying to stand a story up.
Alleged targets of the phone-hacking included former home secretary Charles Clarke, actors Jude Law and Sienna Miller, and former aide to Prince William and Prince Harry Jamie Lowther-Pinkerton, the jury heard. The list also included Lord Archer, cook Delia Smith, and model Abi Titmuss.
Mr Edis said: "It was a perfectly rational but entirely illegal system."
The court heard that the newspaper was tipped off about an alleged affair between Clarke and his assistant Hannah Pawlby, and journalists watched her home and accessed her voicemails.
Although the rumour turned out to be untrue and the paper was "chasing shadows", Edis said it showed the system the tabloid would use.
He said: "The prosecution suggests that Coulson, who is now the editor of the News of the World (NoW), he is not the man who stands outside people's houses hoping to catch them out, he is the man who likes to put the story to people to see what they will say."
He said the NoW used three ways to investigate stories – phone-hacking, surveillance and confrontation.
"The editor is personally involved in the third. Obviously he knows about the second, surveillance, he must do. What about the first? Does he know about phone hacking? He says he doesn't, we say 'Oh yes, he did'."