Photo of Prince William in bikini at party leaked to Sun by Sandhurst instructor, court told 

Prince William started his training at Sandhurst military academy in January 2006 – tips about his course were leaked to the Sun within weeks, a jury has been told. Photograph: Tim Graham

Secret details of Prince William’s military training, including a photograph of him wearing a bikini at a fancy dress party, were leaked to the Sun by a senior Sandhurst instructor “simply to make money”, the Old Bailey has heard.

John Hardy, a former colour sergeant who helped train the royals at Sandhurst military academy, is accused of receiving £23,714 from the tabloid for tips that began within weeks of the Duke of Cambridge’s course starting in January 2006.

Hardy collected £5,000 for leaking a picture of William wearing a bikini underneath a Hawaiian shirt at a James Bond fancy dress party, the court heard, and another £250 for “spying” on colleagues at a lap dancing club.

Prosecutor Michael Parroy QC told jurors that Hardy acted “in direct and flagrant breach” of army orders when he leaked information about the princes to the Sun’s chief royal correspondent Duncan Larcombe.

“It was done, we say, abusing the position of trust he held, simply to make money,” he added.

Hardy was described by Larcombe as his “eyes and ears at Sandhurst” when seeking authorisation for payments to the army officer for confidential details about William’s training.

Parroy told jurors that the first known contact between Hardy and Larcombe was on 23 December 2005 – a month prior to Prince William’s arrival at Sandhurst. Two months later, Hardy was paid £500 for leaking Prince William’s training schedule, the court heard.

The timetable gave Larcombe an “inside track” on Prince William’s whereabouts, jurors heard, and meant the journalist was able to book trips to Wales and Cyprus to “spy” on the royal during training.

Hardy was paid £1,000 for leaking an official army picture of a fellow Sandhurst instructor who had been accused of killing a police officer, the court heard.

Another £500 payment was made to Hardy for a story about Prince Harry completing a “fearsome army drill” with a bayonet, jurors were told.

In one case, Larcombe requested £250 in cash so that Hardy could go to a party at a lap dancing bar organised by Prince Harry’s army instructors.

In an email, jurors heard that Larcombe described Hardy as “my most important Sandhurst contact” and “without doubt my eyes and ears at Sandhurst and is extremely important to me”.

“He has a bundle of information for me about William’s movements during next term and on his adventurous training next week,” the journalist wrote.

Parroy said the contact between Hardy and Larcombe in the first months of Prince William’s training in early 2006 was “very, very regular, sometimes several calls a day” and lasted until October 2008.

Larcombe, Hardy and his wife, Claire Hardy, deny being involved in misconduct in public office between 9 February 2006 and 16 October 2008.

Alongside them in the dock are three senior Sun journalists, former deputy editors Fergus Shanahan, Geoff Webster, and chief reporter John Kay.

They are accused of paying £100,000 to senior a Ministry of Defence official, Bettina Jordan-Barber, for stories between 2004 and 2012.

Earlier on Thursday, jurors were shown dozens of stories, allegedly fed to Kay by Jordan-Barber, including details about the deaths of British troops in Afghanistan, an indecent images scandal at a military college and an army officer who stripped naked and led a drunken congo dance.

The court heard that Jordan-Barber produced an internal-only MoD briefing about the incidents before leaking the restricted details to the Sun. She was paid thousands of pounds for the stories via Thomas Cook transfers, jurors were told.

Parroy said: “Those payments were made at a time when they most certainly should not have been; without any sort of query about whether they should have been paying a public official. All they were interested in, we suggest, was the stories.

“The fact that other newspapers were following the Sun, which was in the lead because of Ms Jordan-Barber and her relationship with Mr Kay, did not meant that the revelations made were lawful or the payments made were lawful or the process was a proper one.”

Bringing the prosecution’s opening to a close, Parroy said the “corrosive” stream of leaks invaded people’s privacy, endangered national security and generated an “atmosphere of suspicion and of mistrust” between Sandhurst cadets and their instructors.

The six-figure payments to Jordan-Barber and the Hardys amounted to a “serious abuse of the public’s trust”, he said. “The behaviour of both the sources and the newspaper is corrosive and detrimental to the vital relationship and trust between public and state in matters that concern them directly and indirectly.”

He added: “The constant intrusions of the media led to a good deal of extra work for those involved with the princes’ security.

“Clearly it was evident that someone, and probably more than one person, was willing to let down both the princes and the academy by selling stories.”

Kay, Shanahan, and Webster, deny a charge of conspiring with Jordan-Barber to commit misconduct in public office between 2004 and 2012.

Webster denies a separate charge of conspiring with an unnamed army officer to commit misconduct in public office between 3 November 2010 and 6 November 2010.

The trial, before Mr Justice Saunders, is due to last three months.