By Martin HickmanDetectives are carrying out a live investigation into whether a senior Army officer leaked a photograph of Prince William in a bikini to the Sun, the phone hacking trial heard today.An email from a Sun journalist discussing a payment of £4,000 for the image, taken at a fancy dress party while the prince was undergoing his military training, referred to it coming from "William's direct platoon commander."Giving evidence, Detective Inspector David Kennett, of the Metropolitan Police, told the court that detectives initially thought the picture may have been handed over by Major Alexis Roberts, who had been Prince William's platoon commander at the time the email was written, on 16 June 2006.However, the jury heard, Major Roberts, who was killed in action in Afghanistan in 2007, and who had been "extremely close" to the prince, had not been the prince's platoon commander at the time of the party, suggesting that another individual was involved.Detectives wanted to interview that officer but he was currently serving abroad and out of the jurisdiction of the Met, the court heard.The Army would not post the officer back for him to be placed "in jeopardy," Detective Inspector Kennett said.He told the court that 60 police officers on Operation Elveden, the inquiry into corrupt payments to public officials, were deployed across "80 to 90" lines of inquiry.Outlining a charge of conspiracy to commit misconduct in public office against Rebekah Brooks while she was editing The Sun in 2006, the prosecution showed the jury an email from a Sun reporter to another Sun journalist.In it, the reporter wrote that a good contact was "offering us a picture of William at a James Bond party dressed as a Bond girl. He is wearing a bikini and an open Hawaiian shirt."The picture, he added, actually belonged to another individual who was "very concerned at the idea of the snap ending up in the Sun." He added: "He also happens to be William's direct platoon commander."The reporter wrote: "The chap who has the picture wants £4,000 upfront."Although an upfront payment was not the way the paper usually worked, the reporter wrote, the paper would not be let down, adding: "Indeed I already have the guy with the picture over a barrel because I already know his identity."The email was forwarded by the second journalist to Mrs Brooks, then The Sun's editor, with the question: "What do you think boss?"Ten minutes later, Mrs Brooks replied: "OK."The Sun subsequently made a cash payment of £4,000 through the Slough branch of Thomas Cook travel agents on 27 June 2006 for a "William in a bikini exclusive."On 12 September 2006, The Sun published a story about the fancy dress party headlined: "Willy in a bikini", with the strapline: "Prince Dresses as Bond Girl." The image was a mocked up picture of Prince William in a bikini.Jonathan Laidlaw, for Mrs Brooks, suggested to Detective Inspector Kennett that a line in the email about "the chap who has the picture" referred to a "third man" whom the police had not bothered to investigate.Inspector Kennett said inquiries had centred on The Sun reporter's contact in the Armed Forces, and the person with the picture, the platoon commander."There's nothing there [in the email] that suggests there is a third individual," he said.Of inquiries into the platoon commander posted abroad, the police were waiting to receive phone data that might prove a link to him. Detective Inspector Kennett said: "Based on the information I know, clearly he would be interviewed."Mrs Brooks, formerly chief executive of Britain's biggest newspaper group, News International, denies two counts of conspiring to commit misconduct in public office. She and the other defendants on trial have pleaded not guilty to all charges, which also include plotting to intercept mobile phone communications and conspiring to pervert the course of justice. The trial continues.