This was recently voted Britain's funniest joke:
A woman gets on a bus, carrying her baby. As she pays her fare, the driver says 'Urghh, that's the ugliest baby I've ever seen.' The woman goes to the back of the bus, fuming with indignation, and sits down next to another passenger. She turns to the passenger, and says 'Did you hear what the driver said to me? I was so shocked, I couldn't even speak!' So the other passenger, sympathetic, says 'Never mind, dear, you go back there and tell him what you think of him. I'll hold your monkey for you.
It's official: I'm British. I laugh every time I hear the punchline.