The story I posted makes it pretty plain that the slippers were distributed at Frogmore. The following sentences mention the marquee on the grounds. And- can you honestly imagine that a party the Queen hosted at Windsor involved slippers?
Could someone point me to a source for the Suits cast not being invited story?
Yes, that why I needed a moment when I thought the cast of Suits weren't invited to Frogmore. It's one thing to have bowl food, but I can't see the Queen taking it that far.