to June 11, 1953 and Trooping the Colour with the Queen Mother, Princess Anne and Princess Mary all in memorable designs.
If there are any hats worn today, please share them in the comments.
Images from Getty as indicated
Royal Hats
The Bold, Beautiful and Bizarre World of Royal Millinery
Royal Hats 
Anne’s hat (and coat?) in color. She wore it the following year, when meeting HM during the Commonwealth Tour.
May 5, 1954: Malta
Embed from Getty Images
The Queen Mum’s hat is actually quite glam. Princess Mary as usual looks like someone has just dropped a hat on her head.
This is a lovely photo.
Youtube has one very poor color video of the 1953 Trooping the Colour, and the Queen Mother appears to be wearing a white feathered creation. Sure enough, 2 months earlier, she wore the same hat, described as a white ostrich hat.
https://www.alamy.com/apr-04-1953-queen-mother-at-nuffield-foundation-reception-london-a-image69282179.html
I’m guessing 1953. A lovely photo.
It says 2003. I do not think the year is correct.