A review of the threat level posed to the couple has been ongoing and has not led to a change in security arrangements.
But the King is believed to have intervened to offer his own resources so the couple can bring their two children Archie, seven, and Lilibet, five, over for their first visit in four years.
Harry, who stepped back from royal duties when he moved to California, lost a legal case against the Home Office last year when it downgraded his security.
He later said it was not safe to bring his family to the UK.
TENSE REUNION
Meg’s UK return is astonishing – she’s made life tense for King, expert says
But this week a “safe return” for a five-day visit was said to now be possible after “changes” to security arrangements.
However, sources said the Government’s Royal and VIP Executive Committee had not upgraded its threat level.
A Government spokesman said of its protective security system: “It is our long-standing policy not to provide detailed information on those arrangements, as doing so could compromise their integrity and affect individuals’ security.”
Buckingham Palace and the Sussexes, scheduled to be at Harry’s Invictus Games in Birmingham, declined to comment.
Harry, Meghan and their children will return to the UK for the one-year countdown party for the Invictus Games.
The multi-sport event for veterans is his signature charitable initiative and a project deeply personal to his life and military career.
The family visit comes amid continued efforts to repair relations between Harry and his father.
Last September, Harry and the King held a long-awaited reunion at Clarence House during one of the Duke’s visits to Britain for charity work.
Although the meeting was brief, it was their first face-to-face encounter in 18 months and raised hopes that ties between the pair could begin to heal.
Harry has returned to Britain several times since stepping back from royal duties in 2020, but Meghan and the children have almost always remained in California.
The Prince was last in the UK for his two-day hearing at the Court of Appeal in London, while Megan hasn’t set foot in the country for nearly four years.
The upcoming trip would be Meghan’s first major public return to the UK since attending the Queen‘s funeral.
Since Harry and Meghan relocated across the Atlantic, King Charles has only seen his grandchildren in person once.
While Archie spent much of his first year living in Britain, Lilibet was born in California after the couple’s move to the US.
Her only visit to the UK came in 2022, when she celebrated her first birthday with family and friends at Frogmore Cottage in Windsor.