It was a large, square, stiff envelope, and I initially concluded that someone had sent me an especially elaborate Christmas card. But no - miss_newham, who works In The Music Industry, had sent me a 7" single of the Skyfall theme by Adele!
Thank you ever so much - it was a lovely surprise, and I have filed it with the rest of my 45rpm Bond collection.
(You didn't think I had a collection of Bond singles? Fools.)