to this day in 1941 when Queen Elizabeth, The Queen Mother, and King George VI visited the London & North Eastern Railway’s Doncaster Works in Yorkshire. The Queen’s jaunty hat with upswept brim is the basis for a very familiar hat shape we often see on royal heads today but clearly, one that is not as contemporary as we might think!
Photo from Getty as indicated
Royal Hats 
If I recall, the appearance from the front was more toque-like than sliced, but yes, definitely the fore-runner of the saucer worn on the side!
As if we found the original source of the hat… love it
More pics, and a short video. The front underside of the hat’s brim is very detailed. Love the addition of the brooch.
https://www.iwm.org.uk/collections/item/object/205202692
https://www.iwm.org.uk/collections/item/object/205202691
https://www.iwm.org.uk/collections/item/object/205202689
https://www.iwm.org.uk/collections/item/object/205202710
https://www.iwm.org.uk/collections/item/object/205202688
Thank you so much for posting this video!
Love the hat and the whole ensemble.
Fantastic footage, thank you Mcncln! Great hat, would love to get my hands on it to see how it’s made!