By Martin HickmanRebekah Brooks's PA had no idea there was a police investigation into phone hacking at the News of the World until the week the paper closed, the Old Bailey heard today.Giving evidence at the phone hacking trial, Cheryl Carter said that she knew nothing about Operation Weeting despite detectives arresting three senior News of the World staff in the Spring.Mrs Carter, Mrs Brooks's PA from 1995, told the court: "I didn't know any of that. I wasn't privy to that."She said she only found out about the police investigation on 4 July 2011 when the Guardian broke the news of the hacking of Milly Dowler on Monday 4 July 2011. The News of the World printed its final edition on 9 July 2011.Mrs Carter made her comments as she was questioned about an email recovered from her BlackBerrry by police in which she said she urged News International’s IT department not to keep any of Mrs Brooks’s iPads.The court has previously heard that up to eight of Mrs Brooks’s iPads, iPhones and BlackBerries are missing.In the exchange on 20 June 2011 – six months after the launch of Operation Weeting – Mrs Carter informed Mrs Brooks her iPad was being replaced and that a new one was on order.Mrs Brooks replied: “Has all emails on.”Mrs Carter emailed her back: “Everything is being transferred to the black one… They’re only giving you that one because I have told them they must not keep any old devices.”Andrew Edis QC, for the Crown, told Mrs Carter that at the time there was a police investigation ongoing into hacking - “and you knew that.” He added that police had been in the building regularly and three high-ranking journalists, whom he named, had been arrested.But Mrs Carter, who planned to emigrate to Australia before she was arrested in January 2012, said she “not been privy” to that.Mr Edis asked: “To the police investigation?”, to which Mrs Carter said: “I didn’t know they were in the building at all.”Asked: “When did you find out about the investigation?” she replied: “When Milly Dowler was hacked.”Mr Edis asked: “4 July?”, to which Mrs Carter replied: “Yes.”Mr Edis continued: “You worked for the chief executive whose job it was to deal with all this sort of thing – but you never knew anything about it?”Mrs Carter replied: “I never knew… I’m saying that is the truth.”Later, she was asked whether Mrs Brooks had had “lots of BlackBerries.”Mrs Carter told the jury: “They quite often broke or she [Mrs Brooks] dropped them in water.”She said that News International’s IT department would have kept the broken devices.Mrs Carter, who left News International in July 2011, denies conspiring the pervert the course of justice by allegedly removing Mrs Brooks’s notebooks from News International’s archives earlier that month.Mrs Brooks, her boss for 16 years, also denies that charge and charges of conspiring to hack phones and to commit misconduct in public office.