60 years ago to the December 19, 1961 christening of the now Earl of Snowdon. Princess Marina of Kent and Princess Alice, Countess of Athlone, attended in a pair of very memorable pillboxes!
Image from Getty as indicated
Royal Hats
The Bold, Beautiful and Bizarre World of Royal Millinery
Royal Hats 
They look like they have seen it all, they dressed the part, had fun shopping for the pillboxes
and after the christening they want a sherry.
The Countess of Athlone had some fab hats in her long life. I love that she took the bus around London to go shopping later in her later years; I just wish I could find the photo I saw of her once waiting at the bus stop (it probably was in some random book).
Of course Marina looks chic as always.
I know the photo you mean. It was in Majesty magazine a few years ago. Was incongruous in the surroundings.