Sherlock, Series 01, Episode 01, A Study in Pink
Dr. John Watson: What are you doing?
Sherlock Holmes: Nicotine patch. Helps me think. It's impossible to sustain a smoking habit in London these days.
Dr. John Watson: That's good news for breathing.
Sherlock Holmes: Ah, breathing. Breathing's boring.
Dr. John Watson: Is that three patches?
Sherlock Holmes: It's a three-patch problem.
Like a five-pound note (a fiver) or a ten-pound note (a tenner)