In fact, all of the ladies on the invite list will be.
The future queen consort will have to wear a hat. Not a fascinator, Not a hairband. Not a feather on a clip. A hat.
All of the women at Harry and Meghans wedding will have to wear one, including Queen Elizabeth II, Camilla Parker Bowles, Princess Anne and Meghans mother Doria Ragland, to name a few.
What is a queen consort?
A queen consort is the name given to the wife of a reigning king.
William is guaranteed to be King one day, given he is second in line to the throne.
Kate will share his social rank and status when he becomes King, although not his military or political powers.
It means while Kate is juggling Charlotte, George and their third baby, who is due this month, she must also remember to pop on a hat or shell be shown the door.
While the royal females will all be decked out in hats, it is not a rule exclusive to the royals.
The Anglican Church requires women wear hats to religious events, such as christenings or weddings, but this is not a rule strictly adhered to by many church-goers.
It is linked to a passage in the Bible from Corinthians when St. Paul says in 1 Corinthians 11: 1-34: I want you to understand that the head of every man is Christ, the head of a wife is her husband, and the head of Christ is God.
Every many who prays or prophesies with his head covered dishonors his head, but every wife who prays or prophesies with her head uncovered dishonors her head, since it is the same as if her head were shaven.
As yet, the Duchess Of Cambridge hasnt publicly spoken out about attending the wedding, but its understood she will be there – with the help of a nanny, of course.
While some might gasp at the idea of potentially having hat hair, Kate seems to be a fan of millinery fashion.
Members of the Royal Family and the Middleton family at Sandringham House after Princess Charlotte's christening pic.twitter.com/P8a5lvfX0n
— Kensington Palace (@KensingtonRoyal) July 9, 2015
She wore one at her sister Pippa Middletons wedding on 20 May last year and baptisms of Charlotte and George.