It's not expressly stated on the invitation, but you're going to be doing the YMCA dance with Queen Elizabeth and that means, no matter how energetic things get on the dance floor, your outfit should take this into account. You'll notice that both Kate and Meghan favor closed-toe pumps when they're on royal engagements, and that's because the queen would never approve of bare toes! Sheer hosiery is also the norm (though Meghan herself has broken this rule!).