The former editor of the Daily Mirror has been interviewed by police investigating alleged phone hacking.
A 51-year-old understood to be Richard Wallace went to a police station in south London around 1pm and was questioned by detectives from Operation Weeting, Scotland Yard's investigation into phone hacking.
Mr Wallace was deputy editor of the Sunday title between 2003 and 2004, before taking over at the Daily Mirror for eight years.
This follows the arrests on Thursday of four current and former Trinity Mirror journalists in early morning raids.
People editor James Scott and deputy editor Nick Buckley were held, along with former editor of the Sunday Mirror Tina Weaver and former deputy editor of the newspaper Mark Thomas. They were all released on bail until April.
Scotland Yard said the alleged conspiracy is being treated separately from the two plots being investigated at the now defunct News of the World, and its inquiry is focused on the Sunday Mirror in 2003 and 2004.
Officers said they plan to make contact with potential victims of the suspected phone hacking in due course, and have appealed to anyone who thinks they may have fallen prey to get in touch.
Trinity Mirror confirmed on Thursday that Mr Scott and Mr Buckley and two former employees had been arrested. A spokesman said: "We are co-operating with the police and we have no further comment to make at this stage."
Four civil claims have been lodged against the Mirror Group over alleged phone hacking, which it is contesting. In the company's results, the firm said it has applied for two of the matters to be struck out entirely and has challenged the general basis for the other two.
Media lawyer Mark Lewis is dealing with phone-hacking claims for four high-profile individuals including former England football manager Sven-Goran Eriksson. The three other claimants were Coronation Street actress Shobna Gulati, Abbie Gibson, former nanny for the Beckhams, and Garry Flitcroft, former captain of Blackburn Rovers. Mr Lewis welcomed the news that police are investigating alleged hacking at another newspaper.