Prince Harry is taking legal action against the British government after a decision was made to remove his security.
The Mail on Sunday has revealed lawyers acting for Harry have written a "pre-action protocol" letter to the Home Office. It is understood the letter states they will seek a judicial review if the Sussexes are not provided with continued security while they are in Britain.
This will lead to a battle in the High Court if the case proceeds between Prince Harry and British ministers.
A source told the Mail on Sunday Harry's argument, in a nutshell, is: "You got the law wrong."
"He feels the decision to remove his security was wrong," the source said.
"Pre-action protocol was sent by Harry's lawyers to the Home Office a couple of months ago. This is essentially a precursor to a judicial review."
It is understood the Queen has been made aware of the action taken by her grandson.
Over the week, the Mail on Sunday reported Harry's lawyers issued an "extraordinary statement" defending his decision to sue the British government. The letter also insisted the Prince would not rely on taxpayers to fund his family's security.
The Duke and Duchess of Sussex had been contacted for comment but did not respond.
Harry's most recent visit to Britain in July sparked legal action as his protection had been removed.
"When Harry came back last April for Prince Philip's funeral, he was given security. But when he came back in the summer, he wasn't," a source said.
Ahead of his grandfather's funeral, Harry travelled to Britain with his private security team but was greeted on the tarmac at Heathrow by Scotland Yard protection officers.
It is believed that was not the case when he returned in July for the unveiling of a statue of Princess Diana at Kensington Palace.
Princes William and Harry reunited in London for the statue unveiling of their mother, Princess Diana, on what would have been her 60th birthday.
The brothers put their tension aside as they were all smiles for the service at Kensington Palace, pulling off a green cloth to show the statue of the late Princess with her arms around two children, a boy, and a girl, with a third child also in the background.
Following the reception, the Prince left with bodyguards thought to have been provided at his own cost.
This case is believed to be the first time a member of the Royal Family has brought a case against the Queen's government.
This article was first published by the NZ Herald and is republished here with permission.