Prince William failed to inform his senior officers of the “true nature” of a helicopter flight which he used to attend a stag party on the Isle of Wight.

The prince was on a four-month attachment to the RAF when he made the contentious flights in April. Neither the Chinook helicopter crew, nor his station commander, knew that the real purpose of the trip in the £10m aircraft was to transport him to a social event.

Senior officers would not have permitted the trip if they had been told the full details, according to documents obtained by newspapers under the Freedom of Information Act.

The prince, codenamed Golden Kestrel, flew five questionable flights at a cost to the taxpayer of £86,434. The first, on April 2, was from RAF Odiham to Highgrove House, the official residence of his father Prince Charles, which William then “buzzed”. The next day he flew to Bucklebury, Berkshire, landing in a field owned by the father of his girlfriend Kate Middleton.

A day later he flew to Hexham, Northumberland, where he landed. Another pilot flew the helicopter back and the next day the prince attended a wedding on the Scottish border town of Kelso of Iona Douglas-Home, a friend from St Andrews University.

On April 9, he piloted the Chinook to London, landed and flew on to RAF Cranwell before returning to Odiham.

His final flight, on April 11, involved flying to London where he collected Prince Harry before flying to the Isle of Wight for the three-day stag party of Peter Phillips, his cousin and the son of the Princess Royal.

An e-mail dated six days later and sent from an Odiham officer to a superior makes clear the prince’s training project officer and crew were unaware why William made the Isle of Wight flight. “Convention during his stay has been not to inquire into his time off duty,” it said.

If Group Captain Andrew Turner, station commander at RAF Odiham, had been aware of “the true nature of the weekend, the sortie would not have been flown and alternative means of transport would have taken Prince William to the Isle of Wight” the e-mail continued.

Last night a Ministry of Defence spokeswoman said the flights were legitimate training sorties. “In retrospect, there was a degree of naivety involved in planning these sorties but there is no question anyone misled anyone,” she said.

A spokesman for Clarence House said: “Prince William takes his share of responsibility for what happened.”

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