Jackie and Pete in “Rise of the Cybermen”

Have a look! [she shows him a banner that says "Happy 40th Birthday"]

What's wrong with that?

40! It says 40!

You are forty!

Well, I don't want the whole world telling, do I?

You're having a party tonight!

My thirty-ninth! My official biography says I was born on the same day as Cuba Gooding, Jr., and that makes me thirty-nine, thank you very much.