Now here’s an intriguing question for the weekend.

We received an email about Royal fertility tests for women intending to marry a senior Prince. I think it merits some careful consideration.

It’s known that this practice has traditionally been part of the process of the marriage ritual of heirs, or very near heirs, to the Throne. Diana had to undergo a medical examination and we know that it was successful.

What, though, if someone failed? These days the hurdles are much higher than even 20 years ago. It’s not just a Yes/No verdict that’s available. DNA testing can throw up a mass of probability data over a wide range of genetic diseases.

Where does the fail point lie: a one in ten chance, one in 100, one in a million? Most people would probably fail if the criteria were set too high.

Now here’s the rub. How would the Palace handle a situation where a young women was generally fertile, but who had a mild to medium chance of producing children with some genetic disability?

Obviously, they wouldn’t splash it all over the press. If some journalists discovered the truth, editors would be very wary of putting private medical information into the public domain. There might even be general agreement across the media not to publicize it at all.

And how would this play into the current situation of both the heir’s heir and the spare’s long-term girlfriends?

This is a hypothetical question, but one which will make life very difficult in the future for the Royal Family and pose a variety of ethical and practical questions in an age of maximum media exposure.

There are strongly positive noises coming from Clarence House on the love(ish) match between Prince William and Kate Middleton — the girl who won’t go away.

A Clarence House insider said: “Kate being given a pass to Clarence House is a very clear and practical step towards putting her relationship with Prince William on a more official footing. It’s a logistical way of bringing her into the fold. Things are a lot more imminent than you understand. Plans for William and Kate have been ring-fenced.”

“Ring-fenced” is certainly a step up from “pencilled-in”, the last phrase we heard from Palace sources on this matter. Since then, the couple have gone through a series of ups and downs, ons and offs and general confusion.

The words, “Things are a lot more imminent than you understand.” strongly suggests an announcement of their engagement very soon, perhaps as soon as they have returned from the Seychelles.

I can’t remember such openness from senior Palace sources before. We must now expect a third engagement among the Queen’s grandchildren in short order. And there’s also Zara waiting in the wings until after the Beijing Olympic Games in 2008.

It looks like wedding cake is going to feature on every Royal menu for the next year.

The Sunday Mirror is reporting that Prince Harry has asked long-term girlfriend Chelsy Davy to marry him, and, apparently, she has said yes.

The Prince is said to have popped the question on a recent safari holiday in Botswana. “However, they do not intend to become officially engaged until Chelsy finishes her post-graduate course in politics at Leeds University and Harry has served the Army overseas.”

Chelsy, 21, is currently recuperating after an emergency appendix operation at home in Cape Town. She is said to be planning to spend weekends with Harry at Highgrove in Gloucestershire when she moves to Leeds next month.

A friend said, “[Harry] has come to realize that what he and Chelsy have is pretty special.”

However, the couple have decided to keep a low profile with Chelsy out of the public eye as much as possible. She will not be attending Princess Diana’s memorial service at the end of August.

So, an engagement at last in the Royal Family. How far behind will Willam be, I wonder?

In a new book, The Diana Chronicles, Tina Brown, former editor of Vanity Fair and Tatler, gives a damning indictment of Diana’s character and life.

Brown claims to be a friend of the late Princess, having lunched with her in New York just weeks before she died. The book, written to coincide with the 10th anniversary of her death, is set to be a bestseller on both sides of the Atlantic.

The book is significant because of the number and quality of the people who have spoken out for the first time. It comes out just two weeks before the Concert for Diana in July, and must be causing her two sons and the organizers some considerable consternation.

Since we don’t yet have a review copy of The Diana Chronicles, here are a few juicy snippets gleaned from a newspaper account, from which you’ll gather Tina Brown didn’t think very much of her :

“Diana was a spiteful and manipulative neurotic.”

“Diana wanted a ‘guy with a Gulfstream’ [a private aircraft]”

“She loved Charles’s title more than him.”

“Charles did love Diana and wanted her back.”

“She did not throw herself downstairs [when pregnant, as she claimed in the Morton book].”

“Diana ogled herself in newspapers.”

“She would never have married Dodi.”

Strong stuff, which adds to the mountain of contradictory reportage available on her life. When accounts of a person vary quite so much as Diana’s do, it usually reflects a person who tries to be all things to all people.