It’s about time we revisited this almost ancient storyline which was once so huge, but now just perks up a tad on the few occasions they are spotted together.

Prince William and Kate Middleton’s relationship is now so low key that it survives in the public mind only on the memory of what happened more than two years ago. Nothing of substance has been added since then. In fact, Carole Middleton’s negative comments appear to have downgraded it further.

Despite that, some journalists still call Kate “William’s girlfriend”. Could that be because no other girlfriend has been in evidence?

Richard Kay’s comment on Channel 4 that Kate has become a kind of smokescreen, allowing William to play the field, begs some questions.

If they are “just friends” it would be to her advantage to go along with it and remain in the Prince’s circle.

Publicly, Kate’s status is non-defined, neither one thing nor another. That’s not a good place for a bright 27 year-old to be.

Wild speculation has now given way to yawning apathy. For William, that’s not a good situation either. He will need a store of popularity to perform his role in future years.

Has his new publicist team decreed a Trappist-like existence for the Prince? Or is it William’s decision to stay out of the spotlight?

As for Kate: if a particular species of bird becomes rare, then not sighted at all, in most cases it’s become extinct.

That would be a pity though.

On Wednesday evening, Prince William attended a gala evening of music and food in London to mark the end of his year as Patron of the Lord Mayor’s Appeal.

The constantly solo Prince suggests that Kate Middleton has resumed her role as casual girlfriend rather than the “Girlfriend,” to which she had been promoted, according to recent reports, with the consent of the Queen.

The Grand Finale of the event was at St Paul’s Cathedral in celebration of the end of the appeal for 2008.

Money was raised throughout the year for Wellbeing of Women, which funds research into women’s health, and Orbis, which works to prevent blindness in developing countries.

David Lewis. the Lord Mayor of the square-mile financial district, who should not be confused with Boris Johnson, the publicly-elected Mayor of all London, said of the occasion:

“I have had such a wonderful and exciting year with tremendous support from many people and organisations in the City. I am delighted that many of our friends have joined us to celebrate the Grand Finale to my Lord Mayor’s appeal.”

William now steps down as the Appeal’s Patron.

Quite what this quiet period in Kate’s role signifies for the future is not yet crystal clear. My guess is that the high spot of the relationship has passed and an enduring friendship has replaced it.

The Prince will be fully occupied from January with an 18-month spell of intensive training as a helicopter pilot with the RAF’s Search and Rescue unit. The belief is that he will make the grade and go on to serve for up to six years in various remote spots around Britain, and possibly abroad.

Marriage, it seems, is the last thing on his mind.

As for Kate, she is rebuilding her life and expectations within the Middleton family business and, no doubt, will re-emerge into the London night scene as the fancy takes her.

What are Prince William’s motives for choosing the RAF over Kate Middleton?

Whichever way you look at it his motivation for deciding on four more years in the military is hard to read. The choice is made more puzzling by his apparent sudden change of mind.

Just a few weeks ago William seemed set to spend 2009 learning about constitutional affairs, interspersed with some Royal engagements and other duties. Although it was never explicitly spelled out, most observers had pencilled in a summer wedding with Kate Middleton.

Then, anonymous voices claiming inside knowledge began to put it about that marriage had been postponed for 18 months at least. No reason was given, which made the claims less credible at the time.

Last week the absent bits of the jigsaw puzzle fell into place. William had decided to train for the RAF’s Search and Rescue unit and was intent on becoming a helicopter pilot on active duty around Britain’s shores and wild places.

So what were his motivations, and how does Kate feel about his apparent desertion? The obvious reason is that he enjoys the excitement of service life.

It may also be true that he views marriage as a millstone round his neck. However much he likes being with Kate, it may simply be “the institution, stupid”.

It’s possible that only one of these motives is the real one. Which one would be interesting to know. There’s a lesser probability that both figured in his decision, in which case maybe the French Foreign Legion would be a better choice.

If the first reason is the primary cause of his sudden change of heart, it holds up to the world that he may never be ready to settle down into the boring routine of marriage and Royal duty — at least until he is considerably older.

An even longer life for his grandmother, and an extended reign for his father, might be very welcome to the reluctant Prince.

I’m also beginning to think that Kate may share those views, although not to the extent of being separated from him for the best part of four years.

She may recognize that you have to swallow some bad stuff in order to realize your dreams. As a middle-class female she probably has a better grasp on the realities, like the necessity to compromise a little and settle for what you get.

William, though, as a Prince born to greatness and worldwide fame, may just believe he can have it all without any diversions down unwanted paths and alleyways.

There’s a disconnect somewhere here. Let’s hope neither of the two personalities in this affair gets hopelessly hurt.

It may be that a Christmas announcement is still in the schedule for a May or June wedding next year. In which case the trajectory remains intact. But some sources are warning this is not so, and normal life has been postponed in the foreseeable future.

Since the future of the Monarchy rests on their shoulders, it would be of great assistance if someone known and credible explained the reasons behind this radical change of tack to the great British public.

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.