'We intend to step back as “senior” members of the Royal Family and work to become financially independent, while continuing to fully support Her Majesty The Queen.’

It was the bombshell to end all bombshells: the announcement made by the Duke and Duchess of Sussex on January 8, 2020, that they were to leave the UK.

But why? Why give up the castles and the parades, the pomp and the pageantry, the status and the security? Why demote yourselves from the most influential family on the planet? What on earth drove Megxit?

Several reasons were given. It was the intense media scrutiny. Friction with the Cambridges. The bossy ‘men in grey suits’ at Buckingham Palace. None of this seemed fully convincing at the time. Was it really such a torture to live as duke and duchess?

Now, I believe, we have come closer to the truth about what really led to Megxit: the cloud of suspicion surrounding Thomas Markle Snr, and the impact this must have had on Meghan.

It was in early 2019 that the Met Police shared a letter with the duchess accusing Markle Snr of heinous crimes. She was around six months pregnant. Looking at pictures of her from that year – shaking hands, doing walkabouts, going on tours of Morocco and southern Africa – it seems remarkable that she kept a sunny smile plastered to her face at all times.

This was a woman not only adjusting to life as a full-time royal and new mother, but also to the news that her father was quite possibly a paedophile. What agonies lay behind the smile? Even for a professional actress it must have been an enormous strain.

Of course, Markle Snr has not been proven guilty of anything yet. But judging from their estrangement and the statement Meghan released last week saying that she had kept her children separate from their grandfather ‘to protect them’, she has clearly long believed he has a very dark side.

Thomas Markle was often the primary parent, the one who took Meghan to ballet and tap-dancing classes

Before the estrangement from her father, Meghan paid tribute to ‘the blood, sweat and tears this man invested in my future'

It was in early 2019 that the Met Police shared a letter with the duchess accusing Markle Snr of heinous crimes

Just think for a moment about how devastating this discovery must have been. Images of Meghan as a girl with her father underline their closeness. He was often the primary parent, the one who took her to ballet and tap-dancing classes. Before their estrangement she paid tribute to ‘the blood, sweat and tears this man (who came from so little in a small town of Pennsylvania, where Christmas stockings were filled with oranges, and dinners were potatoes and Spam) invested in my future so that I could grow up to have so much’.

In that famous Netflix documentary, the duchess said: ‘I was a daddy’s girl all my life.’ In his memoir, Spare, Prince Harry said that Meghan ‘still, even in her 30s, called him Daddy. She loved him, worried about him – his health, his habits – and often relied upon him.’

The shock of that letter in 2019 must have been sharpened by the fact that, within a few months, she had Archie. Many will remember the emotions unleashed by the birth of your first baby. The intense protectiveness, anxiety, even paranoia. To find out that her own protector may well be an abuser must have amplified these feelings. It would heighten the need to feel safe, insulated from the nastiness out there in the world.

It is not hard to imagine that by the end of 2019 this tumult of emotions – horror, sadness, new-mum vulnerability – led Meghan to a series of conclusions: I must protect my child; I must be near the only parent I can trust (mother Doria Ragland, who lives in the US); we must quit the UK.

Perhaps the pressure of public life was the straw that broke the camel’s back, given she was already shouldering the weight of a dark secret that she could not share.

The Thomas Markle accusations reframe other aspects of Meghan’s behaviour in recent years, such as the perfect family image she has curated so carefully. Instagram images of the kids playing in the sun; picking fruit in their Montecito garden; frolicking with the dogs while Mum cooks up a batch of jam in the kitchen.

In retrospect, these images seem less like bragging and more like a riposte to the darkness of her own family background. While the Sussex family snaps seemed like saccharine posturing to many of us, now I get it. What better antidote to the darkness than a wholesome, picture-perfect family life?

These revelations make sense, too, of the somewhat insular life the Sussexes had in Montecito. Many commented on the way their Italianate mansion seemed more like a gilded cage, such as the documentary maker who – having studied their life in the US – said: ‘They seem to have isolated themselves a lot.’ Or the writer on the Montecito Journal who said: ‘You don’t see much of her or him.’

This doesn’t seem so strange now. Meghan’s trust in the father she loved had been utterly shattered. Who could blame her for building walls against the world?

Let us hope that the family’s return to the UK signals a new lease of life for Meghan: freer, lighter, less burdened by the past. It’s been said that the ‘sins of the father should not be visited on the son’ – and nor should the alleged crimes of Thomas Markle Snr scar the life of his daughter.