My grandmother died in 1981, and I only saw this photo for the first time a few weeks ago. It was given to me by my 84 year old aunt, who told me it was something to do with the Bowes-Lyon family which I presume that's what she was told, of course she could be wrong. My gran is the one sitting cross legged far right.
I only know what I was told by my aunt.
Monky