Tonight Channel 4 broadcast an explosive documentary about Prince William and Prince Harry.

Typically for Channel 4 it covered a lot of “toff” activities, like hunting and polo in a deliberately disparaging way, and hyped up every glitch and problem that the Princes endured in their youth.

More interesting were journalist Richard Kay, who was close to their mother Diana, and James Whitaker, the Mirror photographer and lately pundit on all things Royal.

Richard Kay suggested that William is using Kate Middleton as a kind of decoy to cover his other activities. Both Princes, he said, are reluctant Royals who don’t want to do the job.

Whitaker also pursued this line, saying that their decisions to continue in the military “were extraordinary” and indicated they were turning their back on Royal duties and, by implication, marriage.

William does not come out of this very well. We hear that Diana referred to Harry as King Henry because she felt he would be more able to handle the role.

Chelsy Davy’s recent split from Harry was spliced onto the end of the tape, but carried the same message: the Princes are not interested in settling down, and both girls now seem to be aware of that.

Royal Anecdotes has known this for some time, as regulars will know, but the most astonishing assertion, made by Richard Kay, is that Kate is a decoy for William’s private activities.

No doubt a lot of flak will be generated by this documentary, and by the main interviews in particular, so we will await the outcome without commenting further for the time being.

(Overseas readers may be able to watch it on the Catchup service under the title “What happened next”.)

It had to happen, especially after Prince Harry’s decision to devote himself to highly specialized military duties in the Army Air Corps.

Just as his brother, Prince William’s choice of a long stint in the RAF’s Search and Rescue squad all but sidelined long-term girlfriend Kate Middleton, Chelsy, the high-flying lawyer, has backed off and all but dumped the Prince.

It has been clear to Royal Anecdotes for some time that neither Prince was ready to make any commitment to their first lady loves.

Chelsy has clearly been cleverer than Kate in forging a serious career for herself. Her future now seems to be back in South Africa.

A military source is reported as saying, “Harry’s training is going to be seriously demanding and he has been told there will be little time for girlfriends and socialising. He is living in a modest room with a single bed and won’t be allowed to drink from Monday to Friday, and he will need to knuckle down.”

Although Chelsy had planned to join City law firm Allen & Overy after her graduation later this year, she has now told friends that South Africa beckons.

Plainly, Harry’s commitment to the Army has put a lot of pressure on her, since they don’t get much time together. A friend commented, “He’s told her it has to come before anything, and she’s a bit fed up of always coming second. She was prepared to make a big sacrifice by moving to the UK. She had her job lined up and a place to live in London. She’s a very bright girl who wants to be a successful lawyer, but that’s all up in the air now.”

The recent closeness of Chelsy with Kate Middleton may suggest that something similar is brewing between Kate and William. The reluctance of the second in line to the Throne to abolish her “Waity Katie” tag delivers its own message.

Both relationships have run their course. I would expect a similar announcement from the Middleton compound soon.

Unless, of course, William makes an executive decision. Why, then, did he choose the RAF over Kate?

Once again we enter familiar territory: will they, won’t they?

I refer, of course, to that pair of star-tossed lovers, Prince William and Kate Middleton.

They have spent some time together up in arctic Birkhall on the Balmoral Estate in Scotland, causing the usual flurry of anticipation and speculation in the British press and more distant publications around the globe.

I have held off writing about this because I have been here before. Many times before. Too many times before to want to go through the rigmarole again.

However, since events are coming to a head on Friday — Kate’s 27th birthday — and next week, when William begins up to seven years’ service with the RAF, Royal Anecdotes has to say something about the situation.

Firstly, I suspect William joined Charles and Camilla up in Birkhall because of the Queen’s wish not to have the second-in-line to the Throne following the playboy circuit abroad at a time of grave economic stress for her subjects.

The apparent invitation to Kate’s parents, Carole and Michael, may have been out of simple politeness. After all, their daughter has been left dangling for seven years. A Royal expression of favour would make a lot of difference to an ordinary family in extraordinary circumstances.

At the very least Kate’s loyalty deserves a word or two about their future prospects, if only to discourage that dismissive nickname, Waity Katie.

Of course, the elaborate build-up now may be just be a nice way of acknowledging her steadfast friendship without damaging her reputation. As the years of service go by, William would then feel free to find someone else. Kate would more than likely do the same. This feels more like a fanfare and send-off for a Prince about to dedicate a fair portion of his life to dangerous public service.

We won’t know until William is safely tucked up in his new training school. If it hasn’t happened then, it probably never will.

I have to say, there’s very little obvious activity suggesting a Royal engagement right now. But a low-key announcement can’t be entirely ruled out.

Chelsy Davy, Prince Harry’s girlfriend, is currently on a two-week work experience placement at swish law firm Farrer and Co., Lincoln’s Inn Fields in London.

Farrer just happens to be the Queen’s solicitors. They represented her during the recent Queengate row with the BBC. Since the firm only ever takes students from Oxbridge, the work indicates how well regarded Chelsy is with the Royal Family.

Someone close to the scene commented, “These City law firms only ever interview Oxbridge graduates and, normally speaking, someone from Leeds [University] would not get a look-in. This isn’t because the firms look down on other universities, it’s simply because they consider that Oxbridge fulfils all their needs, so why bother to broaden the net?”

Of course, a word in their ear by a figure close to their most prestigious client would not go unheard.

Contrast this with the fate of Kate Middleton, once the leading light of the two Royal girlfriends.

With Kate’s beau, Prince William, signed up to a potential seven years away as a search and rescue helicopter pilot, Kate has disappeared from view. Her job in the small, family party business now seems almost insignificant in comparison with Chelsy’s high-flying London legal outing.

Last week, Kate’s mother, Carole Middleton, spoke to the Daily Telegraph and complained at how her family, its business and her “two other children” were being compromised by the publicity and press intrusions.

Could it be that, in the light of William’s SAR decision, Kate has decided that the relationship is going nowhere, and has quietly called it off for the sake of her family?

It would be a sensible decision for a woman not far short of 30, and the lack of fanfare and open grievance, a relief for the Prince.

Earlier Kate was reported to be going to Sandringham on Boxing Day. It will be interesting to see if that date is kept.