Prohibition on Your 21st Birthday?

Apparently Keira Knightley wanted to celebrate her 21st birthday in a non traditional way. Instead of going out and getting smashed (although I'm sure she got quite pissed) she threw a party celebrating a time when drinking was not a legal activity no matter what age you were! She threw a 20's style birthday party and looked the part to a T. I wonder who her date was? (She looks a little like Natalie Portman here too..Don't you think?)