King Charles' Coronation isn't the only big royal event happening on May 6 - as Prince Archie is celebrating his fourth birthday.
The youngster won't be making an appearance in Westminster Abbey to see his grandfather and Queen Camilla being crowned.
Instead, Archie will remaining at his home in Montecito, California along with sister Princess Lilibet and mum Meghan Markle, who decided to turn down her Coronation invitation.
While the world's eyes will be on Charles, it will be a different story Stateside as Archie will be centre of attention at his "intimate" birthday party.
But there are rumoured fears that the Sussexes could "upstage" Charles' historic day by going large on the celebrations.
Royal columnist Lee Cohen has claimed Harry and Meghan could risk overshadowing his dad's big moment, including the release of a birthday announcement hours before the Coronation.
It is traditional for royal households to release photo portraits on a family member's birthday - with the Sussexes doing this on every previous occasion for their son.
Cohen told Express.co.uk : "It's terribly petty, but the Sussexes, who no longer have their royal platform, seem to relish any opportunity to attempt to upstage a royal occasion.
"It's not as if the Royal Family seek occasions to upstage the antics of the Sussexes, quite the opposite."
Harry is only going to the Coronation ceremony itself at 11am, then is set to jet back to the US on a commercial flight to get back in time to spend time with his son.
A source close to the family has said Meghan's mother Doria Ragland will be at the bash, along with Archie's pre-school friends and some celebrity pals of the couple.
Famous celeb guest who may rock up would be chat show legend Oprah Winfrey, tennis ace Serena Williams, presenter Ellen DeGeneres and her wife Portia de Rossi.
"Harry's going to make every effort to get back in time for Archie's birthday," the insider told Page Six.
"It's going to be an intimate party, it's not going to be like 'My Super Sweet 16' or Portia de Rossi's 50th!"
There will be lots of fun to be had for the kids as the Sussex's grounds extend to a whopping seven acres
They include a playground complete with two slides, climbing frame, tightrope, helter skelter, and two types of climbing wall.
Meghan loves baking at home with Archie, so will no doubt be planning a big cake for her son to enjoy, perhaps even using lemons plucked from their own garden.
Archie's first birthday was a family affair, with Harry and Meghan joined by grandma Doria, while the birthday boy had a yellow party hat on.
"They are celebrating as a family focused on Archie and being together," a source told PEOPLE at the time.
"They'll have a smash cake and Zooms with family and friends. It's been beautiful weather, so perhaps a family stroll with the dogs."
For Archie's second birthday in 2021, Meghan and Harry shared a new photo of their son on their Archewell Foundation website.
The little prince was holding a bouquet of birthday balloons - and it came with a request for fans to donate to COVID vaccine equity for vulnerable families around the world.
Last year, the Sussexes shared a brand new photo of Archie and he received birthday messages from the Royal Family.
On the official Royal Family Twitter account, a picture of Archie as a newborn with his parents and grandmother Doria meeting the Queen and the late Prince Philip was posted.
It was accompanied by the message: "Wishing Archie Mountbatten-Windsor a very happy 3rd Birthday!" It also featured a birthday cake emoji.
Meanwhile, William and Kate opted to share a family photo taken at Archie's christening, which also featured Charles, Camilla and two of the late Princess Diana's sisters.
Their message read: "Wishing Archie a very happy 3rd Birthday today" followed by a birthday cake and balloon emojis.
When it came to Archie's grandfather Charles, his Clarence House Twitter account shared the same picture posted by the Queen's account.
His message to his grandson read: "Happy Birthday Archie!"
It remains to be seen whether the Palace will commemorate Archie's birthday in any way.
There was awkwardness last year as the royals didn't have any new photos of the young prince to share, so reused the old one
It's also been reported that Charles has scrapped plans to honour Archie at his post-procession Coronation lunch.
The original suggestion was that he should make a gracious nod to his grandson by raising a glass, but this is no longer being considered as neither of the Sussexes will be attending.
Harry is set to rush straight off after the ceremony to get back to celebrate with his son, while Meghan has decided to avoid the Coronation altogether.
A source told the Mail on Sunday : "The King considered a toast to Archie. But with no member of the Sussex family now due at the lunch, it is highly unlikely he would do in their absence."
