Meghan Markle and Prince Harry give biggest indication yet that they will NOT attend King Charles's Coronation

However, in a potentially telling move, Meghan and Harry have missed the RSVP date for the ceremony.

The cut-off date was April 3 but staff have still not been told whether the Sussexes will attend despite the Coronation now being just one month away.

Royal insiders are said to be "none the wiser" on whether the couple will attend.

Buckingham Palace has not commented on the Sussexes' non-RSVP but an aide said it was unlikely there would be a strict cut-off date for family members as there would be for other guests.

A source told the Daily Mail: "Everything is still up in the air and there's only a month to go.

"All people have been told is that 'it should hopefully be resolved soon'.

"But in the meantime the teams are trying to finalise plans for 2,000 guests, many of whom are international heads of state and VIPs. It's a headache."

Meghan Markle and Prince Harry's refusal to announce whether they are attending the Coronation has put King Charles in a "heartbreaking" limbo when it comes to Prince Archie and Princess Lilibet, according to a royal author.

Prince Archie and Princess Lilibet will not have a role at the Coronation due to the children being very young.

Prince Louis, Prince William and Kate's youngest child is also expected not to have a role at the Coronation.

However, King Charles has reportedly not invited Archie and Lilibet, instead choosing to extend an invite just to their parents, due to the Sussexes' stalling their decision, royal author Phil Dampier has claimed.

He said: "I'm sure if they had made an early decision to attend and accept the King's invitation with good grace it would have been seen as the first step in rebuilding their relationship, and Archie and Lilibet would have been welcomed with open arms."

Dampier added during an interview with the Mail: "They are too young to be involved in the actual ceremony but of course the King would love to see his grandchildren if they came over and it must be heartbreaking for him that he never sees them."