The Duke of Sussex is reportedly receiving ￡14.5million ($20m) in advance for the book, which will tell his perspective of his struggles within the Firm. He said in a statement that he is writing his memoir "not as the prince I was born but as the man I have become".

       However, his book has already sparked a flurry of reaction online, with royal expert Angela Levin noting that he is likely to speak about his late mother Princess Diana, who tragically died in a car crash in 1997.

       She wrote on Twitter: "I've been told by a well informed source that Harry's memoir will focus heavily on the death of his mother Princess Diana, and who he blames.

       "It was a terrible tragedy but sad the man can't move on."

       The prince will also not be writing the book alone as award-winning journalist and author JR Moehringer is set to be his ghostwriter, who is known for not holding back.

       The Telegraph's Marianka Swain warned the Royal Family that the memoir could "horrify" them, particularly as they are unlikely to find out what Mr Moehringer has written before it is published.

       She wrote: "Working with Moehringer is a statement of intent: that this book may actually have something to say.

       "Readers should be salivating. The Palace should be very afraid.

       "However it came about, it’s bad news for anyone hoping that the royal rift will be repaired any time soon.

       "Nothing is off the table, according to Prince Harry’s description of this 'honest and captivating personal portrait' – not his childhood, public duties, military service or family life.

       "That’s exactly the kind of outspokenness, with the Prince trumpeting his side of the story, that should horrify the Royal Family.

       "But it’s great news for the rest of us. With Moehringer at the helm, this memoir should be teeming with headline-making scoops. As Agassi said of the explosive Open: 'The truth is always surprising'."

       Buckingham Palace has not yet commented on the memoir.

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       2.16pm update: Meghan and Harry humiliated as Netflix deal only intended to 'attract new subscribers'

       Professor Simone Ferriani, an expert in entrepreneurship who specialises in film and media, said he believed there was "not much in" their deal with the streaming giants other than to "leverage" their global brand.

       He told Express.co.uk: "I think there is not much behind it other than the attempt to leverage Harry and Megan’s global brand and attract new prospective Netflix subscribers.

       "Content-wise, I don't think there's any special capability as Harry and Megan's production company - as far as I know - has not developed anything so far, so they literally have zero production experience.

       "More than anything it looks like this is a big marketing hook."

       1.28pm update: Kate Middleton to stay up until midnight tonight for sweet royal tradition

       The Duke and Duchess of Cambridge's oldest son George is celebrating his eighth birthday tomorrow.

       Kate said she likes to stay up late making birthday cakes for her children each year during her appearance on a special BBC programme with baking expert Mary Berry called A Berry Royal Christmas.

       She said: "I love making the cake.

       "It's become a bit of a tradition that I stay up 'til midnight with ridiculous amounts of cake mix and icing and I make far too much. But I love it."

       12.56pm update: Prince Harry told he would not have struck financial deals 'were it not for royal title'

       Royal commentator Richard Kay believes Prince Harry's royal link played a major role in granting him his profitable deals with Netflix and Spotify. In a comment piece, Mr Kay noted the Duke of Sussex isn't the first member of the Firm to write a memoir.

       Former King Edward VIII published his autobiography in 1951 - almost two decades after he abdicated.

       However, Mr Kay claimed the Duke of Windsor needed to tell his story also because he found himself in a tight financial situation.

       On the other hand, the expert believes the Duke of Sussex has been able to become financially independent from the Royal Family over the past months also thanks to the unbreakable links he has had with the Firm since his birth.

       The Daily Mail editor-at-large wrote in the newspaper: "When Edward VIII published his memoir A King’s Story in 1951, he was struggling financially, cut off from the monarchy and without any source of income.

       "With his Netflix, Spotify and Apple TV millions, Harry has no need to earn yet more money.

       "Instead, in what many will see as an attempt to deflect criticism, he is piously promising that proceeds from his book – which will cover his childhood in the public eye, his military life, marriage and fatherhood – will go to charity.

       "Just how charitable the Royal Family will feel towards the wayward Duke of Sussex, with a book that threatens to overshadow the Queen’s Platinum Jubilee next year, remains to be seen."

       12.11pm update: Prince Harry's $20m earnings under question over charity pledge - Duke urged to clarify

       "Obviously we know Harry and Meghan have talked about how they have to pay their own bills now, pay their own security, that their lifestyle is very expensive and so $20million would go some way to paying those bills.

       "They might come out and clarify this and say the advance and the royalties are going to charity.

       "In the UK you have to be very, very clear about which bits of what are going charity but I'm not sure the rules are quite the same in the states.

       "There are still quite big question marks about the financial side of this."

       10.55am update: Prince George's birthday picture: Kate tipped to defy trolls with new snap of royal son

       10.13am update: I can do better! William unveils own new book – hours after Harry drops memoir bombshell

       A definitive guide to the Duke of Cambridge's global environmental competition, the Earthshot Prize, is set to be published in September. William, who is second in line to the throne, has written the introduction to Earthshot: How To Save Our Planet.

       The announcement of William's book comes two days after the Duke of Sussex, who quit royal duties with Meghan Markle last year for a new life in America, revealed he was penning a tell-all memoir about his life.

       The Duke of Cambridge's book features contributions from naturalist and broadcaster Sir David Attenborough, environmental activist Hindou Oumarou Ibrahim, singer Shakira and former astronaut Naoko Yamazaki.

       It highlights the urgency of the environmental challenges facing the world and will showcase some of the solutions taking place.

       The book's publication later this year will coincide with the five-part BBC One TV series on William's ￡50 million Earthshot Prize.

       9.05am update: Prince Harry 'not worried' about losing royal titles as new book set to 'damage monarchy'

       Royal expert Robert Jobson has predicted the book will "impact" the Royal Family when published on the Queen's Platinum Jubilee.

       Speaking to Good Morning America, Mr Jobson said: "I think as night follows day this was going to happen. As soon as he went and lived in the states, I think a tell-all book was expected.

       "I didn't expect it to be coming out in the same year the Queen has been on the throne for 70 years.

       "A time when obviously there is a huge rift with the Royal Family because I can't see any feuds or rifts being healed while you're writing your own memoirs."

       He added: "It has happened before, Edward VIII, when he was Duke of Windsor, wrote his memoirs just before the coronation and that cause a sensation.

       "I have no doubt that this will be a huge hit in terms of sales.

       "I would love to read his perspective but I think in terms of damage to the monarchy it’s certainly going to have an impact."

       8.36am update: Queen to issue Prince Harry with huge lesson as royals prepare to ban Duke from Jubilee

       Buckingham Palace refuses to say whether Harry and his wife Meghan will be invited to take part in the central weekend of events marking the monarch's 70 years on the throne in June next year.

       Earlier reports, before details of Harry's book emerged this week, suggested that the Duke and Duchess of Sussex would be welcome.

       But a palace spokeswoman said yesterday: "We're just not going to get into that. We're not going to speculate."

       7.59am update: Prince Harry ‘must be prepared’ to elaborate on ‘truth bombs’ – claims

       Some royal observers have questioned whether the Duke is set to elaborate on the explosive claims made during his and Meghan Markle’s interview with Oprah Winfrey.

       Richard Kay, editor at large for the Daily Mail, wrote in the publication: “The only explanation for a memoir now must be to capitalise on the publicity and huge fame that he has generated ever since Megxit.”

       He added: “What can Harry offer, apart from a lot of score-settling with the media? In order to justify the vast sums that are being bandied around, it can only be one thing: the book will be a tell-all.

       “He must therefore be prepared to expand on all the explosive ‘truth bombs’ he and Meghan detonated under the Royal Family with Oprah back in March.”