He has been spending precious time with his young family since becoming a father for the first time last month.

But the Duke of Cambridge is reported to have torn himself away from wife Kate and newborn baby George to enjoy a boozy stag weekend with friends.

Prince William was spotted with a group, including close confidante Guy Pelly, travelling in a private carriage from London Paddington to Exeter St Davids yesterday.

A fellow passenger told The Sun newspaper: ‘I walked through the carriage on the way to the buffet car and spotted William with a bunch of chaps swigging beer like it was going out of fashion.

‘The tables were covered with cans and miniature bottles of gin and one chap seemed to be wearing gold lamé shorts.’

The British prince – who was wearing chinos and a smart shirt – returned from paternity leave last week and reported back to work with the Royal Air Force and despite being such a prominent figure, it seems not all passengers realised who he was.

The insider added: “There was an older man next to me who had no idea William was sitting just yards away.

“He nodded towards them and said, ‘There’s a right bunch of lads in there.”