An illegal immigrant from Afghanistan managed to smuggle himself into Sandhurst military academy after hiding in a stairwell next to a coach toilet, according to reports.

The 20-year-old was allegedly able to hide on the Army coach when it was travelling to Britain from 28 Engineer Regiment''s base at Hameln, Germany, on Tuesday.

It is thought he was able to jump onto the bus when it was at Calais, where he travelled among a group of officers and NCOs who did not notice him until the coach arrived at the academy, famous for training Princes William and Harry.

The immigrant was found by a corporal and lance corporal when they got off the bus. Police were called and he was taken away, where he will be fingerprinted and interviewed by UK Border Agency officers.

He will most likely be deported after being sent to a detention centre, unless he applies for asylum.

General Sir Richard Dannatt, the head of the Army, was said to be "incandescent" and has reportedly ordered an inquiry.

A military source told The Sun: "This is an extremely serious breach of security.

"He could have smuggled a bomb inside Sandhurst - or could even have been a suicide bomber, which would have been catastrophic."