Harry ... must now expect intense media scrutiny of his behaviour when he's out in public

Jennie Bond BBC royal correspondent

The director of the industry watchdog, Guy Black, said: "This was an exceptional matter of public interest.

"But this does not detract in any way from the tough rules that apply to all children, including Prince Harry, while they are at school."

BBC royal correspondent Jennie Bond said the prince's privacy at school is likely to be respected, as it has been in the past.

But she added: "Harry has put himself firmly in the spotlight, and he must now expect intense media scrutiny of his behaviour when he's out in public."

'Lesson learnt'

Harry is said to be embarrassed and ashamed about the publicity.

Reports said Prince Charles had sent him to a drug rehabilitation clinic for a day, to shock him, after he admitted taking the drug.

The press watchdog said the story was "exceptional"

The prince - third in line to the throne - had also been drinking heavily at a pub near the family's Highgrove estate in Gloucestershire.

St James's Palace confirmed the prince had "experimented with cannabis on several occasions", but stressed his use of the drug could not be described as "regular".

A spokesman said: "This is a serious matter which was resolved within the family, and is now in the past and closed."

The drug-taking and drinking is understood to have happened over a two-month period last summer, when Prince Harry was 16 and Charles and William were both away from Highgrove.

Rattlebone Inn: Scene of Harry's underage drinking

He reportedly drank at the Rattlebone Inn, Wiltshire - which has since changed hands - and smoked a joint at one of the after-hours parties he held back at the estate.

A friend of the Prince of Wales reportedly told the Times: "Harry hardly touches drink, let alone cannabis, now.

"But you have to ask why the protection officer, who accompanied Harry to the pub, never intervened to stop this sooner."

However, St James's Palace said the officers' job was to protect their charges from danger, not embarrassment.

Blair praises Charles

Prime Minister Tony Blair - whose own son was found drunk in central London at age 16 - praised Prince Charles' "sensitive" handling of the affair.

Harry is said to have 'learnt a lot' at the rehabilitation centre

"The way that Prince Charles and the Royal family have handled it is absolutely right.

"They have done it in a very responsible and very sensitive way."

Prince Charles was reportedly alerted to Harry's behaviour by a member of Highgrove staff, who noticed Harry smelled of the drug.

The Prince of Wales sat down with Harry to discuss the matter, and then asked William to suggest his brother attend Featherstone Lodge Rehabilitation Centre in Peckham, south London.

Sent there to get a glimpse of the dangers of drugs, Harry met with recovering heroin addicts and heard how their lives had been affected by drugs.