Four years after the Duke of Sussex and his American wife Meghan, the Duchess of Sussex, decamped to a villa in southern California, a travel company he controls filed paperwork this week informing British authorities he has moved and is now "usually resident" in the US.

The formal acknowledgment underscores the prince's increasing estrangement from Britain, after he and Meghan walked away from royal duties to pursue lucrative media deals in America.

Since then Harry, fifth in line to the British throne, has repeatedly criticised the royal family, including allegations of unconscious racism that were included in a Netflix series and the prince's autobiography, Spare.

The paperwork was filed by Travalyst Ltd, a company at least 75 per cent owned by Harry and which was founded in 2020 to "to promote global awareness of the importance of sustainable tourism".

The documentation was received on Monday by Companies House, the government agency that oversees the incorporation of UK companies.

The filing further separates Harry from his role as one of his father King Charles' counsellors of state -- members of the royal family who can be deputised to carry out the duties of the monarch if he is unwell or out of the country.

While Harry formally remains a counsellor of state, the Crown informed Parliament in 2022 that "in practice" only working members of the royal family would be called upon to fill in for the monarch.

Although Harry and Meghan have put down roots in the wealthy enclave of Montecito, where they are raising their young son and daughter, Harry is also facing scrutiny about his US residency.

The Heritage Foundation, a conservative think tank, has questioned the Department of Homeland Security's decision to grant Harry a US visa following admissions of drug use that were included in Spare.

The foundation, which has asked a judge to force the department to release Harry's immigration file, argues that the prince either lied on his visa application or was given special treatment because a history of drug use would normally disqualify an applicant from being granted a visa.

Australian Associated Press