Prince William flew a heavy-lifting Chinook helicopter to the Isle of Wight for Peter Phillips’s stag party, it has emerged.

A Chinook Helicoper like William flew costs £35m ($70m)

He flew from RAF Cranwell to Woolwich Barracks in London to pick up Prince Harry before flying on to the Isle of Wight, following his Wings ceremony on Friday. The helicopter’s co-pilot then took the aircraft back to base.

All told the chopper saved the two Princes a six-hour journey through rush-hour traffic and a ferry journey.

Prince William’s RAF commanders defended the flight, claiming it had been authorized and that flying over London and open water was an essential part of his RAF training.

An RAF spokesman said, “Having spent a week under instruction with a Chinook helicopter Squadron Prince William flew a legitimate training sortie which tested his new skills to the limit. Flying at low level Prince William piloted the heavy support RAF Chinook helicopter through the busy London flying lanes to a helicopter landing site in Central London before departing the lanes to the South West, making a water crossing and an approach to a civilian airfield routinely used by Chinook Squadrons. His final flight tested his burgeoning flying skills to the full and he performed very well indeed.”

At the end of all that was a stag party in traditional outrageous style. William was no doubt also celebrating his major achievement of getting his Wings and flying the ultimate military machine to a right Royal party.

William’s future plans include embarking on an intensive course of Royal engagements to prepare for becoming a full-time working Royal in 2009. He will spend two weeks travelling the country on behalf of his charities and meeting members of the public.

The Prince is patron of 14 organizations and is described as being “keen to roll up his sleeves and get stuck in” by publicizing the charities’ work during May.

Updated 16.15 GMT : Contrary to earlier reports, Kate Middleton was at Prince William’s award ceremony at RAF Cranwell today. The BBC has some intimate footage of the golden couple walking along a corridor at the base. Kate looks stunning in her trademark white coat, and the pair seem every bit the fond, engaged twosome. The fact that they allowed such shots suggests their story is moving up a notch or two.

Prince William and Kate at RAF Cranwell

It was all over in an instant. Prince William walked up to the stage at RAF Cranwell and received his flying insignia from his father, the Prince of Wales — who himself had won it back in 1971.

After a four-month attachment with the RAF — normal officer-training takes four years — Flying Officer Wales gained his cherished Wings this morning. The training was to familiarize him with the ethos and methods of the flying service to prepare him for the role of Commander in Chief when he ascends the Throne as King. He also learned to fly fixed-wing aircraft and helicopters.

This wasn’t a Passing Out Parade as we saw at Sandhurst, more like a simple awards ceremony. A proud Kate Middleton watched with obvious delight from the floor, accompanied by William and Harry’s Private Secretary, Jamie Lowther-Pinkerton and their aunt Lady Sarah McCorquodale, who must have been relieved to attend something other than Diana’s inquest.

Prince Charles also bewinged 20 other students at the ceremony.

The night before, a dinner was held at RAF Cranwell, attended by both Princes and the Duchess of Cornwall, to celebrate the achievements of the new young flying officers.

BBC News 24 has been airing live coverage of Prince William’s flying training at RAF Cranwell in Lincolnshire. Here are a couple of screenshots :

Prince William preparing to take off

William takes off on his training flight

As I write, William has just taken off on a training flight which will include aerobatics, a simulated stall and fire onboard, together with an emergency alert. In an earlier photocall, the Prince signified he wasn’t looking forward to the aerobatics.

The weather is not perfect for ground viewing as it’s currently raining with dense low cloud. As William took off, his plane disappeared into the rain cloud.

I would imagine that girlfriend Kate Middleton was watching the live coverage. She will be relieved to know that William is accompanied by an experienced RAF instructor.

Update : We are now hearing that yesterday his instructor “bailed out” on the runway forcing William to fly solo for the first time and earn his “wings”.

Afterwards the Prince said :

“It was an amazing feeling, I couldn’t believe it. I was doing a few circuits going round and round then Roger my instructor basically turned round and said ‘right I’m going to jump out now’ and I said ‘what, where are you going?’.

“He said ‘you’re going on your own’ and I said ‘there’s no way I’m going to do that’ but he said I was ready for it and jumped out. The next thing I knew I was taxiing down the runway and I was sitting there saying ‘oh my God this is a bit odd, there’s no one in here’.

“Once I’d taken off it was fine, you just remember your checks and do all the things you’ve got to do and fly the circuit. Then I was watching the runway getting closer and closer and thinking, please, please don’t mess this up.”

Later, a spokeswoman for British Airways said: “Congratulations to Prince William on his first flight. If he fancies flying a jumbo, he’s more than welcome.”

I think a jumbo-sized beer was much more likely.