Prince Harry can expect to be tested for drugs and could have been disciplined or even expelled by his school, Eton, over his reported cannabis use.

Eton's rules say the head teacher can suspend or expel any boy for having anything to do with illicit drugs - whether in school or during the holidays.

The exclusive independent school's head master, John Lewis, said on Monday: "Any boy possessing, using or selling drugs at school during the term can expect to forfeit his place.

"In cases where concerns exist about a boy's possible involvement in drugs he will be counselled and warned and urine tests are sometimes used to clarify the situation and if possible to put a boy in the clear, which is in fact the usual outcome.

Parental concerns

"If parents have concerns they may express them to the school and (if there is drug use or suspicion of it in the holidays) we would expect parents to deal with it, as was done on this occasion when incidents took place away from the school at the beginning of the summer holiday.

"The school has now dealt with the matter but does not comment on the behaviour of an individual boy which is a private matter between the school, the boy and his family."

In the past Mr Lewis has said that, given the widespread availability of drugs, it would be foolish of anyone in his position to assume that a school population of about 1,290 would somehow "miraculously" be a drug-free zone.

The school's published rules say that every boy must "maintain a satisfactory standard of industry and conduct".

Discretion

"The head master has the power to dismiss or suspend any boy if it should appear to him to be in the interest of the school to do so and in particular to dismiss any boy for possessing, using, supplying or being otherwise concerned in any way with any illicit drug or other harmful substance at any time during his school career.

"The head master may require any boy to submit to a urine or other appropriate test whether on suspicion of the use of illicit drugs or other harmful substances, or otherwise at his sole discretion, and may cause a search to be carried out of any boy's personal possessions or room.

"The head master has the power to treat as a breach of school discipline behaviour during the leaves and holidays of a boy's school career which is liable to bring the school into disrepute."

In more serious cases there is a formal right of appeal.

Eton has in the past expelled sixth formers for smoking cannabis in the town of Windsor, outside the school grounds.