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.