Prince William (pictured, right) and Prince Harry will after all take part in a dangerous 1000-mile charity motorcycle rally through South Africa.

Clarence House confirmed, “The Princes are looking forward to taking part in this arduous motorcycle ride.”

It will be an eight-day ride later this month in an attempt to emulate actor Ewan McGregor and Charley Boorman who rode from John O’Groats to Cape Town in their TV series The Long Way Down.

Now we know the reason Prince Harry attempted and passed his motorbike test after taking an intensive course this summer. It was, it seems, Harry’s idea to raise money for charities, including his own Sentebale, based in Lesotho, and the Nelson Mandela Children’s Fund.

This will not be an easy ride by any stretch of the imagination. The brothers will sleep rough as they cross some of the toughest terrain on the continent.

They will, of course, be accompanies at all times by up to six armed police protection officers.

The ride is being sponsored by Enduro Africa. Each participant will be provided with a Honda CRF 230s, a light 200cc trail bike easy to manoeuvre.

The organizer of the event, Simon Smith, says, “It’s going to be one of the hardest and most demanding things they will ever have done in their lives and at night they are going to struggle to get off their bikes as the pain will be so bad. At times they will be sitting on their bikes looking up at a 60 degree slope wondering how the hell they are going to get up it – not even realizing there is a deep river crossing to get through on the other side.

“It is a very dangerous route and they will undoubtedly collect a fair few bumps and bruises along the way.”

Harry recently returned from training in Canada to be with his girlfriend Chelsy Davy, who needed hospital treatment to remove her wisdom teeth.

William is currently working at the Ministry of Defence, before moving on to the SAS later in the year.

There are more signs of strain between the Royal Family and the Middletons this weekend.

It’s been reported that Princesses Beatrice and Eugenie refused to make space in the front row of a fashion show for Pippa Middleton, Kate’s younger sister. After some embarrassment, she found a seat elsewhere.

It seems that Kate didn’t invite Beatrice to her midnight roller-skating event two weeks ago. Nevertheless, the Princess turned up only to find herself inappropriately dressed.

We also learn that Prince William will be required to spend six years on active service in the RAF following 18 months of training. That adds up to a formidable seven-and-a-half year spell in various inhospitable regions a long way from London.

A chorus of friends and insiders are now claiming that a marriage between William and Kate is off the schedule for at least that length of time.

As Royal Anecdotes suggested immediately after the announcement of William’s decision, a marriage must now be in serious doubt. Extensive preparations by the Palace for a 2009 wedding are said to have been shelved.

As I wrote at the time, all the psychology of this decision fits in with the classic Bolting Bloke Syndrome (our name). He has been with her for so long they’ve become comfortable with each other, but the spark is gone. It’s no longer interesting enough to go the last mile to marriage.

By signing up for a lengthy military service, he creates a wide gap of both time and space between them in the hope the relationship will wither on the vine and fade in the minds of the general public.

The thought may occur that an engagement could still happen at Christmas, as was previously pencilled in, leading to a wedding in the summer. However, would Kate — who enjoys London nightlife — be prepared to live as a service wife in remote parts of Scotland or Wales for seven years, with William out on active duty or standby for much of the time? She would be 35 when he is released.

Again, the psychology says not.

In our view, Prince William has made the decision to move on. It was the only explanation for his announcement, which took everyone at the Palace and Clarence House by surprise.

Kate should move swiftly to shore up her reputation by indicating the relationship is over. Hanging on to an occasional friendship while becoming a laughing stock among her peers, and her gloating enemies, is the worst possible outcome for her.

I believe a wedding was definitely on, and being actively planned for. In the end, William couldn’t bring himself go through with it, but couldn’t end it either. He felt boxed in and made his escape in a helicopter.

Last week Kate was seen out with her first serious boyfriend, a chap who slightly resembles Prince William. He may now be the closest she gets to her Prince.

Clarence House has announced a “star-studded comedy gala to celebrate The Prince of Wales’s 60th birthday.”

I’m not sure how many parties that is now — at least three by my erratic counting.

The press release says it all:

“Comedy greats will help to celebrate The Prince of Wales’s 60th birthday this year with a special one-off comedy show in aid of His Royal Highness’s youth charity The Prince’s Trust.

“The show, called We Are Most Amused, will have a unique line-up with stars such as Rowan Atkinson, John Cleese and Robin Williams on stage together for one night only on Wednesday 12th November.

“The Prince of Wales, who is a keen fan of comedy, will attend the show with his wife The Duchess of Cornwall at the New Wimbledon Theatre.

“Their Royal Highnesses will be treated to a mix of live stand-up and comedy sketches from the world’s greatest comedians to raise money for, and awareness of, the work of The Prince’s Trust which helps to provide opportunities for disadvantaged young people in the UK.

“For the first time in over 25 years, stand-up comedy legend and Hollywood star Robin Williams will perform on a UK stage. Monty Python founder and comic genius John Cleese has promised something extra special in honour of The Prince’s birthday and after a long stint on the small and silver screens, British comedy great Rowan Atkinson will return to the live stage.

“The line-up will bring together the very best in comedy talent – from much-loved established names to fresh young acts from the stand-up circuit – a combination which will appeal to all ages and, above all, to comedy fan and guest of honour The Prince of Wales.

“With further acts to be announced, We Are Most Amused promises to be a night to remember and will be screened on ITV1 shortly after the live event.

“We Are Most Amused will take place on Wednesday 12th November 2008. Tickets will go on sale at 10.30am on Wednesday 1st October and prices range from £25 to £100. To purchase tickets either call 0870 060 6646, go online at www.newwimbledontheatre.co.uk or visit the New Wimbledon Theatre Box Office in person.”

It sounds like great fun, if you like that sort of thing.

In a surprise announcement from Clarence House this morning, it has emerged that Prince William will not leave the military next year to become a full-time working Royal.

Prince William preparing for a flying mission

He will instead leave the Army and become a full-time member of the RAF’s Air, Sea Search and Rescue team, flying Sea King helicopters.

We understand he will serve for a minimum 30-36-month period, plus 18 months of training, totalling more than four years. He will be 30 or 31 when he finally hangs up his sword.

The work will involve hazardous rescue operations, winching people to safety from cliffs, ships and open seas in all weathers.

In a statement, Prince William said, “It has been a real privilege to have spent the past year understanding and experiencing all aspects of the British Armed Forces.

“I now want to build on the experience and training I have received to serve operationally — especially because, for good reasons, I was not able to deploy to Afghanistan this year with D Squadron of the Household Cavalry Regiment. The time I spent with the RAF earlier this year made me realize how much I love flying.

“Joining Search and Rescue is a perfect opportunity for me to serve in the Forces operationally, while contributing to a vital part of the country’s emergency services.”

In the next few weeks he will become the first member of the Royal Family to train with the elite special forces regiment, the SAS. He will also spend time with the Special Boat Squadron, the sister regiment of the SAS, and the Special Reconnaissance Regiment.

It’s obvious that Prince William is not yet ready to resume civilian life and cut the chord with the military. Like Prince Harry he enjoys the rough and tumble of serving with the Armed Forces, but is frustrated he’s not able to join his regiment on the front lines of the two wars they are fighting.

The Air Sea Rescue mission seems an ideal — if hazardous — alternative.

The question of his marriage therefore hangs in the balance. A training period of 18 months accords with several broad hints released to the press that he won’t be marrying for that length of time.

However, it is not beyond the bounds of possibility for him to take a month’s leave from training next summer to accommodate a wedding and honeymoon.

Since Air-Sea Rescue is British-based, Kate could easily live with him in married quarters, whether in Cornwall or Scotland. In those circumstances, nobody could accuse the second-tier Wales’s of shirking their duty to the nation.

Otherwise, the prospect of a wedding mid-2010 is the next window of opportunity, with a very distant date at the end of his service as the last resort. I can’t believe Kate would be willing to wait that long.

Of course, the 18-months line may just have been spun to divert attention from a Christmas announcement.

As always, we shall have to wait and see.