"I wouldn't want to ruin our friendship by overstepping a line. And sometimes it's hard to tell what the borderline is between flirtatious and offensive."

The Doctor studied her seriously. "I can trust you to tell me if I'm getting out of hand assuming a general set of borders, but I don't know where the borders are." He took a piece of garlic bread and waved it at her. "Will I offend you by eating this? The book was rather emphatic about what you shouldn't eat on a date, but if I can't trust the book...."