How old am I?

It's always fun to have people guess your age. Most guess under, which I suppose is the polite social norm. Today was wild though: met a Finnish girl (24) on the Tube home who guessed at ... 19. That's right folks, me, a teenager. After I allowed her a second guess it crept up to "no way are you older than 21". Yeah, baby! Needless to say she received the kiss she so richly deserved at that point...