I don't believe he figured it out. It looks to me like the queen said something to him. Possibly "set it down."
I like how Camilla starts to giggle when she realizes he actually made her look classy. She pulls it in quickly, but you know she's loving it.
Neither Princess Anne nor Prince Philip were wearing good poker faces during that dinner.
Anne looked like she was sucking on a lemon and Prince Philip smirked at an early comment Obama made about his British heritage through his mother. Later Philip he was obviously snoozing.