DAY 23 - Wed 27 NovBy Martin HickmanFifteen million emails from Rupert Murdoch’s British newspaper group have been lost to police and other investigators, the hacking trial heard today.

Prosecutor Mark Bryant-Heron explained that the records were wiped during technical changes before a fresh police investigation into phone hacking began in January 2011.

Prior to January 2005, he told the jury, there had been no archiving of emails by News International, owner of The Sun and the News of the World, meaning that they were lost forever unless they had been saved by a journalist or other employee.

After January 2005, he said, emails would be archived after 14 days, unless they had already been deleted by a user or users.

Mr Bryant-Heron said that there had been a mass “purging” or deletion of millions of emails shortly before the News of the World moved into new offices in Thomas More Square, London, in late 2010.

In August 2010, some 10,363,589 emails dating back to December 2007 were “purged or deleted”. On 20 September 2010, a further 4,480,902 emails were purged or deleted.

During 2010, Rebekah Brooks, then chief executive, responding to a deletion policy set out by the company’s IT executives, approved of removing everything before January 2010. “Yes to January 2010,” she wrote in an email read out to the court. “Clean sweep.”

Later, in January 2011, the court heard, News International called in an outside contractor, Essential Computing, to “extract” the emails of 105 individuals from the system. The court was told they had been converted to “PST” files.

At the conclusion of the prosecution’s statement, Judge John Saunders told the jury not to worry if they had not understood the technical information, since it would be explained later in the trial. “It is difficult to follow,” he said of the email deletion evidence.

Mrs Brooks and seven other defendants have pleaded not guilty to all charges. The case continues.