The Queen gave Prince Harry a dressing down for using offensive language about her closest aide, The Mail on Sunday can reveal.
The scolding came after Harry, 35, flew into a rage when the Queen's dresser and confidante Angela Kelly was unable to meet Meghan's sudden demand to visit Buckingham Palace with her hairdresser to try on a tiara that the couple had chosen for their wedding.
When it was pointed out that protocol dictates an appointment must be made to access the Queen's jewels, Harry is understood to have used offensive language about Kelly as he heaped pressure on courtiers to persuade her to travel to London and unlock the cupboard where the tiara is kept.
Kelly learned of the outburst and alerted the Queen to his bad language, prompting the monarch to summon her grandson to a private meeting. "He was put firmly in his place," said a Royal source. "He had been downright rude."
A new biography of Duke and Duchess of Sussex accuses Kelly of "deliberately dragging her feet" when Meghan asked for access to the tiara before the couple's wedding in May 2018.
According to the authors of Finding Freedom, Harry felt that some of the "old guard" at the Palace "simply didn't like Meghan and would stop at nothing to make her life difficult".
But last night a Royal source pointedly said: "The book's version of what happened would not be everyone else's recollection of events and certainly not those who were close to it."
The "tiara row" symbolised the frustration of the Sussexes with the so-called "vipers" at the Palace. Harry saw it as a "huge snub" that Kelly did not organise for Meghan and her American hairdresser Serge Normant to get access to the glittering Queen Mary bandeau headpiece when they wished.
A friend said: "Meg had flown her hairdresser over from Paris for a hair practice and they needed the tiara.
"Angela Kelly said she couldn't come to London and Harry went ballistic. He was furious at the treatment of his then fiancee. Such a snub." But others insist the couple misinterpreted Kelly's reply.
A source said: "Meghan demanded access to the tiara. She didn't make an appointment with Angela, but said, 'We're at Buckingham Palace, we want the tiara. Can we have it now please?"
"Angela essentially said, 'I'm very sorry, that's not how it works. There's protocol in place over these jewels. They're kept under very tight lock and key. You can't turn up and demand to have the tiara just because your hairdresser happens to be in town.'"
Contrary to previous reports, Harry's fury was not about which tiara Meghan was allowed to wear – but about access to it.
"Harry was very quick to let everybody know of his anger and frustration," said another Royal source.
"He let lots of people know that he was unhappy. He tried to get what Meghan wanted by ringing others to put pressure on Angela to bend the rules.
"He was insistent on getting his own way. There was never an appointment that Angela didn't turn up to.
"Harry and Meghan may have wrongly interpreted being told she couldn't have immediate access to the tiara as a snub, but Angela was following Palace protocol.
"It wasn't a snub, it's just the way the institution works."
Regardless, Harry was perhaps ill-advised to criticise Kelly, 61, a docker's daughter from Liverpool, who has risen through the Royal ranks to become one of the Queen's most trusted advisers. She wears-in Her Majesty's shoes and the monarch once told her: "We could be sisters."
The Queen appointed Kelly, nicknamed AK47 because of her uncompromising manner, a member of the Royal Victorian Order in 2006 and promoted her to Lieutenant of the same Order in 2012 for "distinguished personal service".
She is also Her Majesty's Personal Adviser and Curator (The Queen's Jewellery, Insignias and Wardrobe), a role not previously granted to a Royal servant.