By Martin HickmanThe Sun under Rebekah Brooks's editorship had no written rules controlling the payment of money to public officials, she told the phone hacking inquiry today.In cross-examination by chief prosecutor Andrew Edis QC, Mrs Brooks said that there was no need for the newspaper to codify such rules because staff were aware that paying police and other officials was against the law and a code of practice.She told the court that it had not occurred to her that £38,000 cash she approved for a reporter's military source over a five-year period had gone to a senior defence official.In her third week in the witness box, Mrs Brooks was taken by Mr Edis through a series of emails from a Sun reporter requesting her approval for cash payments for his "number one military contact" - who turned out to be Ministry of Defence official, Bettina Jordan Barber.She said that she had not policed the journalist - who cannot be named for legal reasons - because he was so experienced, won awards and had so many contacts."I would not have assumed that [the reporter] had been paying a public official because if we had we would have had a conversation about it," she said.Asked whether it was ever acceptable to pay public officials for information, Mrs Brooks said it was if the information was in the public interest, or if they had come across the information in their private rather than their professional life.But Mrs Brooks, who edited the Sun between 2003 and 2009, said there was nothing suspicious about cash payments in themselves."In the newsroom atmosphere, the cash payments were not seen as criminal or negative or nefarious," she said. "Cash payments were a normal part of the business."She told the Old Bailey: "Maybe it's wrong, but there was an assumption that if a public official was not acting in their duty that wouldn't be wrong."It wasn't something that was invented when I became editor. It's something that's been there always."Asked about the rules controlling such payments, Mrs Brooks said: "We didn't actually have it written down."To one of the reporter's emails, Mrs Brooks had responded within two minutes granting approval and in another within a minute.Mr Edis asked her: "You really were just acting as a rubber stamp, weren't you?" to which Mrs Brooks responded - after a pause - "Yes."She said she had considered each of the reporter's requests for payments for the stories, about military stories in Iraq, Afghanistan and the UK - singly rather than all together, and did not wonder about the identity of the contact.Asked: "It never occurred to you that the source might be a public official?", Mrs Brooks replied: "No."She denies conspiracies to commit misconduct in public office, hack phones and pervert the course of justice. The case continues.