Prince Harry has lobbed plenty of unflattering accusations towards his family in recent months – but there was one in particular that reportedly proved the final straw for King Charles, who swiftly issued an eviction notice to his son and daughter-in-law.

Following the explosive news that Charles kicked the Duke and Duchess of Sussex out of their UK base, Frogmore Cottage, in the days following the release of Harry’s memoir, Spare, it’s now been revealed at which point the King decided his son had “crossed the line”.

Sources told The Mirror that Harry’s claims against his stepmother, Queen Consort Camilla, and his depiction of her as “the villain” in TV interviews promoting the book had “outraged” Charles.

The UK publication claims the new monarch was handed a dossier of details about what was included in Spare shortly after its release on January 10, and began the eviction process from the five-bedroom Windsor estate property the very next day.

 “It was the last straw. Harry was well aware how Camilla would be a red line for his father and he crossed with flagrant disregard anyway,” the source told The Mirror.

“The King felt without a doubt it crossed a line. It was the ultimate act of disrespect.”

Frogmore Cottage was initially given to Harry and Meghan as a wedding gift from the Queen, but following extensive renovations, they ended up living in it for less than a year before announcing they were quitting royal duties and moving overseas.

LONDON, ENGLAND - SEPTEMBER 19: King Charles III and Prince Harry, Duke of Sussex follow the coffin of Queen Elizabeth II as it is carried into Westminster Abbey on September 19, 2022 in London, England. Elizabeth Alexandra Mary Windsor was born in Bruton Street, Mayfair, London on 21 April 1926. She married Prince Philip in 1947 and ascended the throne of the United Kingdom and Commonwealth on 6 February 1952 after the death of her Father, King George VI. Queen Elizabeth II died at Balmoral Castle in Scotland on September 8, 2022, and is succeeded by her eldest son, King Charles III. (Photo by Hannah McKay- WPA Pool/Getty Images)

It’s understood the couple – who have been based in Montecito, California, since 2020 – have been given until the coronation in May to remove the last of their belongings from their former home.

It’s also been reported that Charles suggested that his brother, the disgraced Prince Andrew, move into Frogmore Cottage instead.

• King Charles evicts Harry and Meghan from Frogmore Cottage, Andrew may move in
• 'Kick him out': Andrew facing eviction
• Monarchy NZ: Princess Anne's visit is a real opportunity

However, The Sun reports that he is so far “resisting” the offer to downgrade from his nearby Royal Lodge mansion.

Last month, it was revealed that the Duke of York was “distraught” over the prospect of being “evicted” from his palatial home in Windsor, with a dramatic cut to his yearly earnings looming from April. Andrew, 63, currently lives with his ex-wife, Sarah Ferguson, in the 30-room mansion in Berkshire, which is about 5km from Windsor Castle – his home since 2004.

Harry’s onslaught of allegations in Spare and his promotional interviews included that his stepmother had planted stories in the press. Photo / Getty Images

Harry’s onslaught of allegations in Spare and his promotional interviews included that his stepmother had planted stories in the press to make herself look better after marrying Charles in 2005 following a highly publicised affair.

“Certain members have got in bed with the devil to rehabilitate their image, but that rehabilitation has come at the detriment of others,” Prince Harry said in an interview with ITV.

In another interview with US programme 60 Minutes, he confessed he wanted Camilla to be happy so she could be “less dangerous”.

“She was the villain. She was the third person in their marriage. She needed to rehabilitate her image,” he told host Anderson Cooper.

In an interview with US programme 60 Minutes, Harry confessed he wanted Camilla to be happy so she could be “less dangerous”. Photo / Getty Images

The Mirror also claims Charles was furious at Harry’s suggestion that Camilla had plotted to marry him.

“Shortly after our private meetings with her, she began to develop her long-term strategy, a campaign directed at marriage and … the Crown (with the blessing of our father, we supposed),” Harry wrote in Spare.

“Stories started appearing in all the newspapers about her conversations with Willy, stories which recounted lots of small details, none of which came from my brother.”

Despite that, sources close to the couple have revealed they were “stunned” by Charles’ decision to evict them – and had the support of “at last two members of the royal family” who were “appalled” by the move.

Harry, Meghan and their two children at Frogmore Cottage. Photo / Netflix

“Harry and Meghan have until early summer to vacate,” a source told Finding Freedom author Omid Scobie in an article for Yahoo7 News. “Initially, they were given just weeks, but now they have at least until after the coronation.”

Scobie claimed that the King was “spitting mad” after Spare hit bookshelves, and communication between Harry and his family has now hit “an all-time low”.

“It all feels very final and like a cruel punishment,” a friend of the couple told the outlet. “It’s like [the family] wants to cut them out of the picture for good.”

Scobie also described Frogmore Cottage as the “only sufficiently secure refuge in the country” for Harry, Meghan and their two young children, after they lost access to UK police protection in 2020.

The Windsor property is covered by the Royalty and Specialist Protection Unit.

-Bronte Coy, news.com.au