Here are three royal hats worn on this day by three generations of the British royal family. While the timeline here covers sixty years, we still see iterations of these hat styles and shapes today.
Queen Mary, February 12, 1932
Queen Elizabeth in Kuwait, February 12, 1979
Princess Diana in India (wearing a Philip Somerville design), February 12, 1992
Photo from Getty as indicated
Royal Hats 
Hats From The Past is such a blast! It’s Diana for the win! She really suited wide-brimmed hats. The next best is Queen Elizabeth’s hat, which has an interesting shape and trim. It’s always good to see her in something other than the mainly tall crown with a short brim hats she mainly favours today. The photo of Queen Mary’s hat isn’t that clear, so it’s hard to judge.
Queen Mary’s hats used to be described as Toques, a name for the style that doesn’t seem to be used any more. She was unable to modernise her style of dress because her husband liked her as she was.
You can always look at the growing Glossary of Hat Types here on the blog. This definition of a toque hat might be helpful!
I suspect that Queen Mary’s hat has a round crown and and a ruched bumper brim, similar to this hat.
Embed from Getty Images
Re the 25 bells hat, for Halloween that year my sister wore to work (over her clothes) a pink peignoir and a pink silk(y) curler cap with pink styrofoam egg carton cups tied on. She looked like an exact match. Apart from that tidbit, I adore Queen Mary and all her hats.
Pictures please!
Queen Mary’s hat looks too Cossack like for my taste. Queen Elizabeth’s hat has a shape that suits her very well, and I agree with others who indicated that it is similar to the twenty-five bells hat, which is one of my favorite of the Queen’s hats. I always loved this brimmed hat on the late Diana, Princess of Wales. It was simple, yet elegant.
Queen Mary’s looks like a saucer hat perched flat on top of the head. I am assuming what is underneath it is her hair, unless it is a scarf like material attached to her hat. This would make sense considering how warmly the rest of her is wrapped in fur and the lady behind her. I rather like it but it seems more like a summer hat than a winter hat. I cannot tell if it is straw or felt. That could help with the seasonal appropriateness. Queen Elizabeth’s is strange to me compared to what we see today, especially the material flowing down the back like a waterfall. I love Princess Diana’s hat except the blue on the ribbon and the brim doesn’t match the blue on her dress exactly.
Looking at the photo Queen Mary at some magnification, it appears that it consists of a saucer-like top which surmounts a layer of almost ruched softer fabric, gathered in the front by, or to, some kind of “knot” Whether this last is self-fabric, or a pin or jewel of some kind, I cannot make out. It seems to be worn at a slight angle, and might indeed be somewhat “cossack” in shape.
Now that HQ has educated me through the toque hat in the glossary and additional pictures I understand the shape, but I am not a fan.I am still not a fan of QEII’s hat either. I have a feeling this is an age thing and what I am used to seeing in the last thirty years.
Is the Queen’s hat by Frederick Fox? The shape and style sort of remind me of my favorite — the twenty-five bells.
Diana’s is attractive. It’s hard to see Queen Mary’s clearly.
Love the “Hats from the Past” theme.
Yes, QE2’s hat is reminiscent of the beautiful ’25 bells’ hat, isn’t it? I wish QE would go back to some of her other vintage hat shapes once in a while. I find the ‘stove pipe brimmed’ styles a bit tiresome these days. I love, love, love Diana’s hat. As for Mary’s, it’s of the period and not very remarkable, is it? I just googled for ‘hats of the 1930s’ and a ‘Cossack’ style came up. Maybe that’s what this is.
I’m not sure who designed this hat but it’s certainly from the Fox era so it easily could be his design. It certainly has similarities to the famous pink bells silver jubilee hat!