An upcoming book promises to tell the inside story of how Prince Harry and his wife Meghan, Duchess of Sussex, turned their backs on royal life.

Here's what we know about Finding Freedom and whether the duke and duchess were involved along with some of the biggest things we've already learned.

That's one day later than the UK and USA.

However, you can already get a taste. Multiple extracts have already been published by Britain's The Times and The Sunday Times.

Finding Freedom's publishers say Carolyn Durand (a journalist who has covered the royal family for two decades) and Omid Scobie (the royal editor for Harper's Bazaar) had "unique access" and wrote their book "with the participation of those closest to the couple".

The extracts published so far certainly have a fly-on-the-wall feel.

However, the duke and duchess themselves weren't involved. This is what a spokesperson said in a statement:

"The Duke and Duchess of Sussex were not interviewed and did not contribute to 'Finding Freedom'.

"This book is based on the authors' own experiences as members of the royal press corps and their own independent reporting."

Nevertheless, the authors have been described as "sympathetic" to the couple.

Durand and Scobie write that when Harry and Meghan were dating, the duke sat down with his brother Prince William to discuss the relationship.

According to a source, William, who had only met Meghan a "handful" of times, wanted to ensure Harry "wasn't blindsided by lust".

Harry was said to be offended by this alleged statement from his brother:

"Take as much time as you need to get to know this girl."

Durand and Scobie explain:

"In those last two words, 'this girl', Harry heard the tone of snobbishness that was anathema to his approach to the world. During his 10-year career in the military, outside the royal bubble, he had learnt not to make snap judgments about people based on their accent, education, ethnicity, class or profession.

"Also, to remove Meghan from the equation, Harry was tired of the dynamic that had become established between him and his older brother. There had come a point when Harry no longer felt as though he needed looking after. There was a thin line between caring and condescending. Just because he went about his life differently from his brother didn't make it wrong."

Whether Harry would recognise that portrayal, we don't know, but he did acknowledge tensions last year.

A source also told Durand and Scobie that there was an open invitation for William and his wife Catherine, the Duchess of Cambridge, to visit Harry and Meghan when they were living in Oxfordshire from May 2018 to March 2019, but they never did.

According to Durand and Scobie, Meghan and Catherine only spent a "handful of occasions" together before the 2018 wedding.

"Meghan was disappointed that she and Kate hadn't bonded over the position they shared, but she wasn't losing sleep over it. According to a source, Kate felt they didn't have much in common 'other than the fact that they lived at Kensington Palace'."

But despite the "duelling duchesses" narrative in the media, Finding Freedom says there was no bad blood.

This is how Durand and Scobie describe the relationship:

"Meghan would agree with the assessment that the duchesses were not the best of friends. Their relationship hadn't progressed much since she was Harry's girlfriend. Although Meghan might have understood Kate's wariness to strike up a meaningful friendship, they were still no closer by the time she was a fellow senior working member of the royal family and the wife of William's brother. Flowers for her birthday were nice, but Meghan would far rather have had Kate check in on her during the most difficult times with the press.

"But they were not at war with each other either."

According to Durand and Scobie, a senior royal referred to Meghan as "Harry's showgirl", while another said she came with "a lot of baggage".

It was a similar story with a high-ranking courtier, who was quoted as telling a colleague: "There's just something about her I don't trust."

According to a source, courtiers as well as "some family" also blamed Meghan for the difficulties caused by the Sussexes' push for independence.

Meghan is said to have told a friend in March:

"I gave up my entire life for this family. I was willing to do whatever it takes. But here we are. It's very sad."

That characterisation of the Queen and Prince Philip's reaction was courtesy of "several" members of the royal family.

"The family is very private and bringing it into the public domain, when they were told not to, hurt the Queen," a source said.

The duke and duchess launched the Sussex Royal website, along with an Instagram account, earlier this year, announcing their plans to "step back" as senior members of the royal family, become financially independent, and divide their time between the UK and North America.

Buckingham Palace says Prince Harry and his wife, Meghan, will no longer use the titles "royal highness" or receive public funds under a deal struck for them to step aside as senior royals.

Finding Freedom describes the negotiations that followed, including the "Sandringham summit" attended by the Queen, Prince Charles and William and Harry (with Meghan believed to have joined by phone from Canada).

The deal that followed involved Harry and Meghan giving up the Sussex Royal brand.

But according to a "source close to the couple", Harry's loss of his honorary military appointments hit the hardest:

"That's been a tough pill to swallow, and one that has been most painful to Meghan witness him go through [sic] It's the one that made Harry emotional."

A senior Buckingham Palace aide is also quoted as saying:

"Harry and Meghan would have reached a more beneficial agreement to allow them to live the life they wanted if they had handled things in a private, dignified way."

Read more:

Finding Freedom book extracts claim to tell Harry and Meghan's story, but they say they weren't involved - ABC News