He added that the couple, who stepped down as working royals in 2020, were now 'older, raising two children, building businesses and careers independent of royal life'.

Writing on his new Substack 'Off Script', which he launched yesterday, Mr Scobie said that he was told in 2023 that California was 'not intended to be their only base'.

He added: 'It was the right home for that chapter of their lives, but their children's education and evolving priorities would shape what came next - including where they chose to live, and for how long.'

Mr Scobie reflected on his own experiences under the spotlight and how he also moved from London to California in 2023, three years after Harry and Meghan.

He said: 'Leaving somewhere and returning to it later are not contradictory acts. Sometimes distance is what reshapes the relationship.

'The place you come from can mean something different in your forties or fifties than it did in your twenties or thirties, after years away and as priorities shift.'

Mr Scobie also wrote: 'Harry and Meghan themselves are not the same people who left. They are older, raising two children, building businesses and careers independent of royal life, and relate to Britain differently than they once did.'

He co-authored the 2020 book Finding Freedom, a biography which chronicled the Sussexes in glowing terms and outlined their many frustrations with royal life.

Mr Scobie was at the centre of a royal race row in 2023 when the Dutch translation of his second book Endgame named two royals who were said to have asked what colour skin Harry and Meghan's child Prince Archie would have before he was born.

The book is about an American press agent who leaves behind her career at the White House for a communications job in London at Buckingham Palace.

Following the revelation last Wednesday that Harry and Meghan were returning to Britain, Mr Scobie said the couple have been 'slowly and methodically' planning their move back to Britain.

He added that clues about the Sussexes leaving America after six years 'have been there all along'.

Mr Scobie also mentioned how the duke and duchess had reduced the size of their US office and restructured and rebranded their Archewell Foundation to Archewell Philanthropies.

Mr Scobie told ABC News in a clip he then posted on his Instagram page: 'I think if you've been watching the story really closely, the clues have been there all along.

'We saw earlier this year that Harry and Meghan started to scale down the size of their offices here, the number of staff working for them in the US.

'We also saw them scale down their charitable foundation as well to operate on a different working model. And so you can see then along the way this is a couple that have been slowly and methodically planning some form of move.

'Whether it's the version that was announced yesterday, only they know, but this is definitely a couple that have been looking to make changes, for sure.'

He also posted on his X account for the first time since March, uploading an image of himself looking at the camera with the caption: 'This thing still on?'

In January 2020, the duke and duchess announced they intended to step back as 'senior' members of the royal family, become financially independent, still support Elizabeth II, but split their time between the UK and North America.

The late Queen ruled at the Sandringham Summit, which was convened to resolve the crisis, that the couple could not be half-in, half-out.

By March 2020, they had set up a permanent home in California, officially stepped down as senior royals and stopped using their HRH styles.

But the Sussexes are preparing to set up home in the UK again, in a shock development six years later, with the children now enrolled in British schools.

Former Suits star Meghan is said to be pursuing an acting role, with reports she is in talks about a role in the third series of Guy Ritchie's Netflix hit The Gentlemen, and counter claims that the deal was off.

The duke and duchess are planning an 'extended stay' in the UK, but it has not been confirmed how long this will last.

The dramatic U-turn by Harry leaves many questions unanswered, including whether taxpayers will foot the bill for the Sussexes' security.

Future king William is estranged from his younger brother after Harry criticised him, Kate, Charles and Camilla in a primetime Oprah interview, a Netflix documentary and his autobiography Spare in the wake of his stepping back from royal duties.