SARAH VINE: Anyone fancy a sugary slice of Brand Sussex?

So who lives in a house like this? Come with me now as we go Through The Keyhole and survey the clues left for our grateful gaze by the birthday girl. Over here, a pile of identical white books, their spines carefully arranged in elegant symmetry. Over there, a vase of velvety white roses. On the table, a snowy block of energising quartz.

And is that an Hermes throw I see draped on the chair? Or could the H be a clue for the HRH captured ‘by mistake’ (oh, how we laughed) juggling ineptly in the ‘yard’ outside her window, not quite the court jester, but then again not exactly not, either.

Who knows, if he plays his cards right (and takes his shoes off) he might one day be allowed on to the seagrass, to take a nap alongside the snoozing beagle, to worship at those elegantly turned ankles.

For this is the Queen in her Montecito castle and, I have to admit, it’s very impressive. Very enviable. And so very Meghan.

The rough-hewn sandstone, a hint of regal grandeur, offset by the cosy informality of that off-the-shoulder sweater (cashmere?), that plate of biscuits, that cup of shabby-chic tea.

And, of course, the A-list sidekick, Melissa McCarthy, drawing the viewer in, creating an illusion of casual intimacy. When, of course, it’s anything but. Turning 40 is a significant birthday in any woman’s life but, this being Meghan, it had to, of course, be a SIGNIFICANT significant birthday. She can’t just celebrate like everyone else, throw a party and knock back a few proseccos.

It has to be an opportunity to reach out to the world and, crucially, to enhance the all-important, ever-expanding Brand Sussex.

Forty women, 40 minutes of compassion and caring, 40 chances to help the needy and the disadvantaged.

Not in itself a bad idea – indeed, rather commendable. But the problem is, this is Meghan.

And, however much I try, however much I want to believe she’s genuine, and that she is only doing this for the sisters, I’m afraid the snake of cynicism uncoils itself out of shot and whispers: ‘This is a masterclass in image management.’

Genuine? Not after the past few months. Not after everything she and Harry have said and done to hurt those closest to them – and not after they have proven themselves such arch hypocrites.

Admittedly, things may look different Stateside. I’m sure the duchess’s American audiences – and they, after all, are the only ones she really cares about – will lap this latest performance up, gorge themselves silly on her saintly sincerity.

But for me it’s going to take more than a sycophantic celebrity sidekick and some guff about female empowerment to convince me that this is anything other than what my gut tells me it is: a carefully orchestrated PR exercise.