William is studying history of art

The Press Complaints Commission chairman is warning newspaper editors to continue to leave Prince William alone after his 21st birthday next month.

A 1995 agreement between St James's Palace and the press has seen newspapers exercise restraint in their coverage of Prince William and his younger brother Harry in return for controlled access on key occasions.

And Sir Christopher Meyer, who took over as head of the Press Complaints Commission (PCC) in March, is insisting it continues until at least 2004, when William leaves St Andrews University, so he can enjoy a reasonably normal student life.

He told BBC One's Breakfast With Frost programme the "very common sense and robust arrangement between editors and St James's Palace allows some access for them to Prince William, to know what is going on in his life and to take the odd photograph, in return for which we don't get a paparazzi feeding frenzy".

In September Prince Edward apologised for breaching William's privacy

"My message to the two sides is keep that understanding going because it is in both your interests."

William needed to "finish his education at St Andrews in relative tranquillity so he can get his work done and get his degree," Sir Christopher told the programme.

The PCC had "very very sharp teeth" and would use them "when the need arises", he added.

William is in his second year at St Andrews, in Fife, where he is studying history of art.

In March, St James's Palace told the PCC it took a "dim view" of the News of the World newspaper publishing photographs of William strolling down to his local pub, shopping at Tesco, riding his mountain bike and chatting to friends.

OK! magazine was censured over snaps of William in Chile

In September last year, the Palace condemned the "insensitivity" of a TV movie aired in the US which dramatised the years from the death of his mother, Princess Diana, to his arrival at St Andrew's.

In 2001 Prince Edward promised to stop making TV programmes about royalty following controversy over his production company's filming of Prince William at university.

A royal row blew up after staff from the company were discovered filming William, Edward's nephew, during his first few weeks at St Andrews.

All other photographers and film-makers had by then left the town in line with a request from the Palace.

The media has been warned to be sensitive over Prince Harry, 18

The celebrity magazine OK! was censured by the Press Complaints Commission in 2000, after it published unauthorised long-lens pictures of Prince William on a trip to Chile.

The media has also been warned in the past about their treatment of William's younger brother Harry, now 18, after allegations of under-age drinking and drug-taking.