The News of the World found out that Prince Harry's then girlfriend Chelsy Davy was bombarding him with calls and texts when he was training at Sandhurst, a jury at the Old Bailey heard today.
The royal editor of the now-defunct tabloid, Clive Goodman, sent an email to editor Andy Coulson in August 2005 saying she was blitzing him with calls.
In the email Goodman wrote: "He's not allowed to use his mobile at Sandhurst until he's off duty but she's blitzing him with dozens of calls and texts when he should be concentrating on his training."
Harry could only field the calls when he had finished his training duties at 10pm, the email said.
The court has heard claims that the newspaper used phone hacking to get stories on the royals, including a claim that Harry broke rules at Sandhurst by asking an aide for help with an essay.
Jurors have been told that a story titled "Harry's aide helps out on Sandhurst exams" came from a voicemail illegally accessed by private investigator Glenn Mulcaire for Goodman.
The story came from a voicemail message left by Harry for his private secretary Jamie Lowther-Pinkerton, asking for information to help with an essay, the court has been told.
Goodman, 56, from Addlestone, Surrey, and Coulson, 45, from Charing, Kent face two allegations that they conspired together and with other unknown people to commit misconduct in public office between August 31 2002 and January 31 2003, and between January 31 2005 and June 3 2005.
Coulson is also accused of conspiring to hack phones between 3 October 2000 and 9 August 2006.
That charge is also faced by former News of the World and Sun editor Rebekah Brooks, 45, of Churchill, Oxfordshire, Ian Edmondson, 44, of Raynes Park, south west London and former managing editor Stuart Kuttner, 73, of Woodford Green, Essex.
Brooks also faces two counts of conspiring with others to commit misconduct in public office - one between 1 January 2004 and 31 January 2012, and the other between 9 February2006 and 16 October 2008 - linked to alleged inappropriate payments to public officials.
She also faces two allegations of conspiracy to pervert the course of justice - one with her former personal assistant Cheryl Carter, 49, of Chelmsford, Essex, between July 6 and 9 2011, and a second with her husband, Charles Brooks, and former News International head of security Mark Hanna and others between 15 July and 19 July 2011.