SARAH VINE: Where DO Harry and Meghan stand in relation to this puppet of theirs? If the Duke and Duchess of Sussex don't denounce the poison in Omid Scobie's new book, we can only assume they endorse it

Despite all the provocation, Buckingham Palace has so far maintained a dignified silence on the latest 'revelations' in Omid Scobie's new oeuvre, Endgame, which finally hit bookshops yesterday following weeks of carefully orchestrated 'leaks'.

That is undoubtedly the wisest course of action for the King. To engage with this absurd Sussex sycophant would only lend credence to his claims, dragging the Royal Family even deeper into the never-ending Harry and Meghan psychodrama.

Whether that will change now that the Dutch edition appears to have 'accidentally' revealed the identity of the alleged 'royal racist', who is supposed to have commented on the colour of baby Archie's skin — remains to be seen.

But when it comes to the Duke and Duchess themselves, they do need to let it be known where they stand in relation to this puppet of theirs.

Because the more coy they are about the truth of their relationship with Scobie, the more they lend credence to the notion that the poison in his book leads back, ultimately, to them.

Harry and Meghan's silence is effectively an endorsement of his status as their 'unofficial mouthpiece' — and, by extension, an endorsement of all the petty, vicious and malicious accusations he makes.

In no particular order: the Princess of Wales was liked by the late Queen on account of her allegedly biddable nature, which led to her being described as 'Katie Keen'. That is not a nickname I've ever heard applied to Kate — although she was described, rather cruelly, as 'Waity Katie' before her marriage to Prince William, giving the lie to the notion she had a much easier ride than Meghan.

There's more. The Princess of Wales is apparently just a 'part-time royal' on account of the fact that she likes to spend time with her three young children in the school holidays.

She's also, apparently, terrified of doing anything other than 'grinning photo ops', which is a bit rich seeing that all the Duchess of Sussex seems to do these days is... grinning photo ops.

And at least the Princess of Wales does hers for charity, whereas the Duchess of Sussex seems to spend most of her time posing alongside celebrity friends. But let's not split hairs.

My point is that this nonsense has to stop. Either the Duke and Duchess denounce this effluent and its source, Scobie, or the general public on both sides of the Atlantic will have no choice but to conclude that, in the parlance of U.S. political campaigns (and make no mistake, this is political), they fully endorse Scobie's message.

Why they would associate themselves — even tacitly — with such a person is anyone's guess. Perhaps because, having attacked the Royal Family in a full- frontal assault via their interview with Oprah Winfrey, their Netflix documentary and Harry's memoir, Spare, the world still appears somewhat sceptical of their one-sided account.

Maybe Scobie's book is one last throw of the Sussex dice, a desperate — and increasingly hysterical — attempt to reclaim the narrative in the War of the Windsors, which in recent months has made them seem increasingly surplus to requirements.

Because the truth is that the Royal Family is doing just fine without them.

In an ideal world, the Duke and Duchess of Sussex would have remained working royals, and no doubt they would have made a positive contribution. But since they left, making sure to trash the place on their way out, the institution they so despise and deride has not crumbled to dust as they might have hoped. Indeed, if anything, it seems to have gone from strength to strength, despite arguably one of the greatest setbacks to have befallen it in decades — the death of Queen Elizabeth II.

While Meghan and Harry have been moaning from their Montecito mansion, the remaining royals have quietly got on with the job, apparently drawing closer together in adversity.

The King and his elder son — who, it's been said, have not always seen eye to eye — appear to me much more aligned. I dare say that has something to do with the fact that they have both been on the receiving end of Prince Harry's ire, as have their spouses.

If, in the past, the Prince of Wales felt his loyalties were in any way divided between his father and his younger brother, the latter's appalling behaviour has put paid to that.

In particular, the way Prince Harry has attacked both Queen Camilla and the Princess of Wales — casting them almost as the ugly sisters to Meghan's Cinderella — has infuriated both men, and understandably so.

It may also have played a part in bringing Camilla and Kate closer. There's a new warmth and ease between them, a camaraderie even, that was very much in evidence at this year's Remembrance Sunday service at the Cenotaph.

As two women whose support is vital to the success and wellbeing of their husbands, they not only have a shared experience, they also (unlike Meghan) understand exactly what is required of them — and undertake the assignment with grace, dignity and admirable consistency.

And it's this, perhaps, that is at the core of this endless sniping — either straight from the horse's mouth or via agents such as Scobie — that continues to emanate from Camp Sussex, despite the passage of time.

Remarkable when you think about it, but it's been almost four years since they left, demanding that their privacy be respected while at the same time invading that of almost everyone else in their family, including the late Queen. By now, the Sussexes could surely have moved on — after all, they've got the freedom and independence they wanted. But it seems they just can't.

Why? The answer, I believe, is glaringly obvious. Having stormed out, in their arrogance and complete lack of self-awareness, they believed that the Royal Family would never survive.

They surmised that without their stardust, it would become a tarnished, dull, old institution that interested no one.

The awful reality for them is that precisely the opposite has happened. The British monarchy is thriving: re-invigorated, even. The King has stepped into his mother's shoes with solemnity, and he and his Queen have confounded the naysayers by showing themselves to be hard-working and diligent.

The Prince and Princess of Wales have not put a foot wrong — and less prominent royals such as Sophie — the Duchess of Edinburgh — have also stepped up to the plate.

Everyone is doing just fine without the Duke and Duchess of Poor Little Me, thank you very much. They must be spitting tacks. After all, it wasn't meant to be like this. They were supposed to ride off into the sunset and the whole thing was supposed to collapse without them.

But it hasn't turned out that way. Hence, perhaps, these latest, desperate, laughable character assassinations from their 'mouthpiece', Scobie. Are the Sussexes trying to stay relevant? If they are, no one's interested. The world has moved on, and we've all got better things to do.

The only people this book damages are the Sussexes themselves. Not just because it makes them seem like a pair of embittered has-beens, jealous of those who have succeeded through hard work and persistence where they failed.

But also — and this is the sad part — because the longer they continue silently to endorse these attacks, the deeper the rift between Prince Harry and his family becomes. And the less likely the chance of there ever being a reconciliation.