Former News of the World editor Andy Coulson's deputy has become the latest of a string of journalists to go on trial for plotting to hack phones of celebrities.
Neil Wallis, Coulson's right-hand man between 2003 and 2007, is accused of being part of the scandal which led to the Sunday tabloid shutting down in July 2011.
The court heard that it was "inconceivable" that those above and below him in the newsroom all knew what was going on but he did not.
A jury at the Old Bailey was told that Coulson was convicted in the first much-publicised hacking trial but his predecessor Rebekah Brooks was cleared of conspiring to intercept messages.
A number of other staff at the News of the World (NotW) pleaded guilty of the same charge, prosecutor Julian Christopher QC said.
Opening the trial, he said Wallis was not accused of doing any of the hacking himself, but he knew it was being done and agreed to it.
Mr Christopher said: "The practice was so widespread at the NotW that it is inconceivable that the editor above him should have been involved, and those below him should have been involved, without him also knowing about it and being involved."
A phone-hacking journalist would recount one occasion when Wallis and Coulson were both played a taped voicemail recording setting a story in motion, he said.
And Wallis was included in a number of emails which referred "obliquely" to hacking, the prosecutor said, adding: "All those involved in the email plainly knew what was being referred to."
Wallis, 64, of Chiswick, west London, denies conspiracy to hack phones.
The jury was told that the phrase "phone hacking" was coined after the arrests in August 2006 of royal correspondent Clive Goodman and investigator Glenn Muclaire, who was paid around £100,000 a year by the NotW.
Searches of Muclaire's premises and a NotW safe revealed a number of recordings of voicemails.
The pair admitted hacking later that year but the conspiracy went further, the court heard.
Three news desk editors, a chief reporter and features editor have since admitted involvement.
Mr Christopher said an analysis of phone records revealed a vast number of calls made during this period on phones attributable to the paper and its staff to the mobile numbers of various celebrities, public figures and private individuals connected to the Royal Household.
Journalist Dan Evans, who was recruited to the NotW from the Sunday Mirror, has admitted extensive hacking and has agreed to give evidence for the prosecution, the jury was told.
The prosecutor said: "He will be able to provide a snapshot of what was taking place at the NotW under the stewardship of Andy Coulson at the top - and his deputy Mr Wallis."