Charles has a 42 person stag 'week'!

Charles and 40 pals fly out for week-long stag do.. but Harry, Wills and his girl start party a day early

PRINCE Charles flew off for a week-long stag do yesterday with his sons and 40 friends.

But that didn't stop William and Harry having a little last-minute warm-up of their own.

To get in the mood, they spent a night out practising for the rave-up at a leading club.

They partied at the Sugar Hut in Fulham, West London, with 11 pals - including Wills' 22-year-old girlfriend, part-time model Kate Middleton.

Kate, in a pink top and jeans, was constantly at Wills' side while inside the club, but diplomatically left 10 minutes after him.

The boys barely had time to sleep it off before - hours later - they and Kate boarded flights to the posh Swiss ski resort of Klosters yesterday.

That's where they were meeting their dad for a last fling before his marriage to Camilla on April 8.

The casually-dressed princes did not join Charles or his fiancee at Birkhall in Scotland for Easter.

The bride-to-be was there with her children Tom and Laura.

And Charles gave Camilla a lift in his private jet - loaned by billionaire John Latsis - after her flight back to London was delayed.

He then flew on to Zurich and was due to arrive in Klosters yesterday evening. New security precautions meant that William and Harry also travelled on separate planes out of Heathrow.

Harry arrived at the resort around mid-afternoon. The first sighting of Wills came when he was driven to a store to hire skis and boots.

A BMW 4x4 with blacked-out rear windows was laid on to ferry the princes around while their friends had to make do with a hotel mini-bus. Wills and Harry are believed to have planned a series of surprises for their dad's stag do.

Sources revealed they have booked one of his favourite restaurants for a dinner - and are preparing some cheeky speeches.

Among those invited to the celebration are Charles's long-time friends Charles and Patti Palmer Tomkinson.

He was one of the guests at Charles's first stag night - held at White's club in London in 1981.

The prince is expected to hit the slopes with his sons today. But he is under strict instructions from non-skier Camilla not to break any bones.

An insider joked: "The last thing anyone wants is for him to have to get married with his arm in a cast."

Charles, Wills and Harry are expected back next Tuesday - just three days before the wedding.