RICHARD KAY: These venomous attacks look bound to snuff out any chances of reconciliation between Harry and William - As Omid Scobie's book is released, a friend of the Prince of Wales says his brother must now 'very publicly distance himself from this'

Until this week, it was just possible to imagine a rapprochement of sorts. Not the warm brotherly affection of old, of course, but a recognition that the best way to secure the future of the monarchy lay in reconciling William and Harry.

There had been talk, admittedly unconfirmed, that Harry and Meghan might be asked to spend part of the Christmas holiday with the Royal Family. And the word from California was that if such an invitation was forthcoming the Duke and Duchess of Sussex would be minded to accept.

How hollow all that soothing talk sounds today with the publication of Omid Scobie's latest biography of the royals in which he turns his malicious attention on the Princess of Wales.

In a thinly veiled but venomous attack, he describes the princess as 'cold', a 'Stepford-like royal wife', while claiming her willingness to support the institution into which she has married has earned her the cruel nickname 'Katie Keen'.

In the same breath, he accuses the mother of three of being a 'part-time working royal' compared with the number of duties carried out by other members of the family.

He also lambasts her for 'advocating for mental health causes while ignoring Meghan's cries for help'. It is not difficult to imagine how Prince William will react to this hatchet-job and harsh depiction of his wife. Indeed, how would any husband respond to such demonstrably unfair claims?

Far from seeking a fraternal reconciliation, such claims from his sister-in-law's cheerleader-in-chief that his grandmother, the late Queen, liked Kate because she was 'coachable', unlike the 'strong-minded' Princess Diana, can only deepen the rift between the brothers.

Not only does this impugn the reputation of Kate, who almost singled-handedly has restored the good name of the House of Windsor in the wake of the crisis precipitated by the Sussexes' petulant Megxit, it simultaneously insults his mother too.

If there is any consolation to be had from this lazy, one-sided version of recent royal history it is that the portrait painted of the princess is so at odds with the facts.

Here is a woman who, in fact, behaves like a textbook royal. She does not show off, she is discreet, she does not complain. When she performs often tedious public engagements she does so with poise and a dazzling smile that gives every appearance of enthusiasm. She is also, thanks to her upbringing, relatable.

Kate instinctively understands that image and image-making is crucially important in the business of defining monarchy and spreading it around the world as an ideal.

Scobie scoffs at all that. To him the princess 'glides under the radar' because she's 'never challenged the system with public struggles or oversized aspirations'. Instead, she is 'comfortable in her role' and has a willingness to bring 'the requisite smile and elegance to her duties as princess', while not being known for 'leadership' or an 'outgoing nature'.

Meghan, naturally, is the polar opposite. He suggests she was 'the new Diana' after marrying Harry, a claim so wild it barely deserves serious examination.

For William, the issue is Mr Scobie's past role as a mouthpiece for the duke and duchess. In interviews the author has insisted he is not their friend, and he has not interviewed them for the book.

What the prince wants to know about Endgame, which is published today, is whether these sour attacks have come directly from within Harry and Meghan's circle.

As one of William's friends, who was also once close to Harry, told me last night: 'It is a matter of trust. The challenge should be for Prince Harry to very publicly distance himself from this.'

Even then few believe the once close relationship between the two can ever be salvaged.

How long ago it now seems when Harry was as close to Kate as he was to William, a relaxed trio delighting the world. The two princes were hardly the first brothers to have a close friendship split by marriage. The tragedy is that before Meghan came along, Harry was the very essence of a popular 21st-century prince. He was what every romantic expected a dutiful young royal to be – not only a brave soldier, but someone who could laugh easily at himself.

Indeed, laughter accompanied him everywhere he went.

Meghan's arrival in his life changed everything. But was this her fault, or was it down to Harry's uncertainty over how best to bring an opinionated Hollywood figure into the restrictive and highly controlled world of royal life?

Meghan, remember, had become accustomed to floating in public her views on everything from climate change and human rights to clean water and gender equality.

This became manifestly clear on the one occasion when the so-called 'fab four' of William, Kate, Meghan and Harry were on stage promoting their Heads Together mental welfare charity, and the Duchess of Sussex naturally dominated the microphone.

There was an air of discomfort about William and Kate as they listened. Here was a young woman making it plain that her new royal status was something to be used so that her voice could be heard – an unknown philosophy in royal life.

At that moment, the silent Kate beside her looked almost dull. In truth, all Kate was doing was following a protocol that has kept the Royal Family in business for generations.

The tragedy is that Endgame looks bound to snuff out those slim chances of royal reconciliation. Instead, 2023 looks like it will end as it began when Harry's own book launched an angry fusilade against his family.