Prince Harry, Meghan and their children, Archie and Lilibet, are believed to have flown into the country privately from California.
They will not return to official duties but will live in Britain as non-working royals. It is thought the family will base themselves at a private property outside of London in the Cotswolds area.
The Sussexes left the UK and stepped back from their royal duties in early 2020, before settling in California in March that year.
King Charles was told of the move earlier this month.
The family visited the King at his Highgrove home in July this year, but it is understood the move was not discussed. Before that visit, Prince Harry and Meghan had not been in the UK together since they attended the funeral of Queen Elizabeth II in 2022.
