So, after all, blood does indeed run thicker than water.

Despite numerous briefings to the contrary, we have finally learnt that Prince Harry flew home to Britain earlier this week to attend the memorial of his uncle, Lord Fellowes.

Although some in royal circles were insisting this does not represent a thaw in relations between Harry and William, the significance of the estranged prince’s last-minute visit cannot be overstated. And as one figure who was close to both brothers told me: ‘Well, it’s a start.’

Not only does it mark the first time this year the brothers have found themselves in a room together, it also provides the greatest indication yet of Harry’s desire to reconcile with the House of Windsor.

Lord Fellowes, who was married to Princess Diana’s sister, Lady Jane, was commemorated at a ceremony in Snettisham, Norfolk. He was one of the late Queen’s most trusted advisers and served as her private secretary between 1990 and 1999, notably counselling Her Majesty during the traumatic Windsor Castle fire in 1992 as well as over the Diana and Charles marriage crisis.

He also had a crucial role to play in the aftermath of the Princess of Wales’s death in Paris in 1997.

It is understood Harry and William sat apart towards the back of the church during the memorial, neither wanting to distract from the sober commemorations.

But what exactly are we to take from Harry’s surprise visit?

Well, firstly, it shows that Harry – like his mother, Diana – sees himself as above all a Spencer. Diana may have had a semi-state funeral as the Princess of Wales, but she was buried as a Spencer at Althorp House, the family seat in Northamptonshire.

And while Harry may be estranged from the Windsors, he has always remained decidedly close with his mother’s family.

Let us not forget that it was his aunt, the now widowed Lady Jane Fellowes, who worked tirelessly behind the scenes to ensure Harry was not isolated following his exit from royal life. As palace doors slammed in Harry’s face, Lady Jane kept a channel of communication open.

Having seen the catastrophic consequence of her sister’s, exit from the Royal Family, Lady Jane knew the importance of looking out for Harry. In attending her husband’s memorial, Harry has been able to pay back a small amount of that kindness.

When Harry’s mother died, it was Lady Jane – along with her older sister Lady Sarah McCorquodale – who attended their nephew’s sports matches at Eton. It was they who ensured Harry received the 13th birthday present the late princess had pre-selected for him. In many ways, Lady Jane and Lady Sarah were surrogate mothers to the young princes.

Indeed, although it has never been officially recognised, it is my strong understanding that Lady Jane is godmother to Harry and Meghan’s son, Archie. She appears in the official christening photos and notably played a significant role in the couple’s wedding.

And more than anyone, Jane Fellowes knows how much her younger sister wanted her two sons to always be close, come what may. So it makes sense she would want to use even her husband’s funeral to be an opportunity for a rapprochement.

But there is another reason why Harry would have wanted to be with his blood family this week.

For yesterday was the 27th anniversary of his mother’s death. A moving coincidence that would not have been lost on any of those in attendance at Lord Fellowes’ memorial the day before.

Each year, since Diana’s passing in 1997, Harry and William have made a pilgrimage to their mother’s grave close to the anniversary of her death. They used to do so together, but in recent years have done so apart.

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That this year they were together again over the week of their mother’s anniversary is deeply symbolic.

Harry would have known this before choosing to attend the memorial. It appears crystal clear to me that he is finally ready for rapprochement.

The question is why, and why now?

There is a very real possibility that the brothers’ attendance – away from the media’s gaze – was orchestrated by Lady Jane and Lady Sarah. Both remain close with the brothers and have long wished to see the two reconciled. However, Harry would also certainly not have attended without the encouragement of his wife, Meghan. It seems there may well be some cold, hard logic coming out of sunny Montecito.

With her media empire a flailing pipe-dream, the former actress knows that her future prospects now rest entirely on Harry’s connection to the Royal Family. That is what makes her relevant. That is what convinces publishers, film producers and podcast studios to print massive cheques in the couple’s name.

In other words, Harry had to go to the memorial to remind everyone of who he really is – or was.

But ironically, the timing of Harry’s olive branch couldn’t be much worse. For in October, the paperback edition of his best-selling and utterly maleficent memoir Spare, hits the shelves.

Typically, publishers like to include new details in the paperback to convince those who bought the hardback to buy the book again.

It’s very notable, however, that Harry has chosen not to include any new stories, certainly none which could further damage the royal brand. He has also decided, as first reported in the Daily Mail, not to give any further interviews publicising the book. And yet, the hoo-ha that will no doubt surround the paperback’s publication is unlikely to convince William that Harry deserves a second chance.

Could Harry have reneged on his contract and convinced his publisher – Penguin Random House – to delay the forthcoming edition? William will certainly think he should have moved heaven and earth to do so.

In the meantime, Harry and Meghan have announced they will attend events at Climate Week in New York next month, something the prince no doubt had on his mind on his way back to California.

King Charles, meanwhile, is understood to have sought counsel from religious leaders as to how to deal with his unruly younger son. I understand the monarch is now open to a truce with Harry – though how easy that truce may be remains unclear.

What is for certain is that Harry’s latest visit to Britain is of great significance. If the prince does succeed in soothing relations with the Royal Family, historians will point to Lord Fellowes’ memorial as a pivotal moment.

Regardless, there is a long road to travel before Harry finds himself truly back in the royal fold.

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