Here we've got the last appearance of Alice Athlone, one of the last surviving grandchildren of Queen Victoria, at a major British royal wedding. She died in January 1981, so she didn't make it to see Charles and Di wed that summer. In this photo, she's just over Prince Philip's shoulder.
Love the purple color and the slight floral-ness of the hat! Here's a better view:
We've got duelling royal Alices in this hattery photo! On the left, in the flowery blue '60s creation, is Princess Alice, Countess of Athlone, a granddaughter of Queen Victoria (actually, the last of her grandchildren to die, for that matter). She was the daughter of Prince Leopold, Duke of Albany; she was also Queen Mary's sister-in-law through her marriage to Prince Alexander of Teck (later the Earl of Athlone). The hat's not bad for the era/wearer; love the '60s fur.
The other Alice here is on the right: Princess Alice, Duchess of Gloucester (mother of the current duke -- that's her husband looking a little bewildered in the middle). I love, love, love her hat here -- I wish this sort of 1960s floral style would come back into vogue. It's so flattering, and the blush color is perfect.