Four months into his reign, King Charles has seen his fair share of drama: two prime ministers and a wave of public attacks from his second son. ‘I would like to get my father back,’ says the Duke of Sussex, in part of a television interview to promote Spare, his book, which is released next week.

The book is, of course, not exactly a sincere appeal for familial unity. It is yet another broadside against Harry’s family, the House of Windsor. The public are by now familiar with Prince Harry’s insights: the royal family’s ‘never complain, never explain’ motto is a deception, he says, as he explains his complaints. The institution frequently briefed, leaked and planted stories against him and his wife, he claims.

Harry and Meghan have for some time been pitching themselves as a superior, more modern and righteous alternative to the corrupt, jealous, borderline-racist institution in London. Exiled in California, the House of Sussex has engaged in all sorts of fashionable causes. For all their resentment of press intrusion, they have sought to build a media business out of their identity – with podcasts, television interviews, books and Netflix shows.

Yet Prince Harry’s repeated attacks pose no serious threat to the monarchy, because his arguments are so thin. He just says the same things over and over again. ‘This is about race,’ declared the trailer to his Netflix series, but Harry and Meghan have not substantiated this incendiary accusation. They make vague hints at some major transgression that they are too dignified to share, but so far that’s it. Polls suggest that the majority of British people do not believe the monarchy is racist. The couple would no doubt attribute that to the entrenched prejudices of the unenlightened British public. But the public remember the welcome British society gave Meghan Markle when she married into the royal family. They also remember that the real fuss came when Harry and Meghan attempted to establish themselves as a breakaway royal branch, under independent management, across the Atlantic.

King Charles has long worried about the royal family becoming too big and unmanageable. He probably never thought that one of his sons would cause so much trouble. Harry and Meghan have become a reverse example of the Queen, who always put the Crown before herself. She took holidays that no one really envied and devoted her life to opening buildings, hosting dignitaries and executing other similar duties. In all the tributes that came after she died in September, an admiration for her humility and modesty was a constant. She never showed off.

By contrast, Harry and Meghan found the reality of royal life insufficiently glamorous. ‘Kensington Palace sounds very regal, of course it does, it says palace in the name,’ says the Duchess in the Harry & Meghan documentary. ‘But Nottingham Cottage was so small… It was just a chapter in our lives where I don’t think anyone could believe what it was like behind the scenes.’

The couple sought out celebrity opulence instead  – private jets, pop-star villas, expensive refurbishments. ‘Censure is the tax a man pays to the public for being eminent,’ said Jonathan Swift in 1703. Members of the royal family have titles, palaces, honorary positions and tax-paying subjects who pay for renovations. The price of this privilege is public scrutiny in a country that has come to expect a certain form of public service in return for royal perks. The Sussexes were unwilling to accept this quid pro quo. So off to America they went.

There really is no more to it than that. Harry could have learned from the Swedish royal Princess Madeleine, who was also a ‘spare’. When she found the royal life unbearable, she married an American and went to live in Florida, exiting the royal family. To her, it was a fair exchange: she forfeited the perks in return for private citizenship. She has not sought a penny from publicity. The Swedish public has heard no more from her, save for her occasional trips home when she visits her family.

Sweden’s constitutional monarchy may provide a model for the sort of royal family Charles wishes to establish: a minimal number of serving members and a clear but firm exit strategy for those who want out.

Harry and Meghan have abandoned their duties without entirely withdrawing from the royal family. They have chosen to earn money by milking the Duke’s name and regularly repeating grievances. Harry has suggested that some of the proceeds for his $20 million book will go to charity, but the couple have not said the same about the $100 million they are understood to have received for their tell-all Netflix series.

But how long can Harry and Meghan keep reselling their story of separation from the monarchy? The tale is already getting rather tired: told first to Oprah Winfrey, then again at painstaking length over the Netflix series, and now through Harry’s book. Each interview and new disclosure – or repetition of previous disclosures – only underlines how little they really have to say.

Harry’s behaviour shows why his father was right that the future of the monarchy is for it to become smaller. The challenge for the King is to resist being goaded into a public rebuke. ‘Recollections may vary’ – the Queen’s answer to Harry’s sound and fury – was the perfect response. Nothing more needs to be said.