D - Do you know who the prime minister is?
C - Obama.
D - No, he's the president in the US.
C - Oh. Tony Blair?
D - No, but he was A prime minister.
C - That Brown bloke. Gordon Brown.
D - Getting closer. Do you really not know who it is?
C - Nick Clegg?
D - He's the deputy.
C - Okay then. Who is it?
D - David Cameron.
C - Never heard of him.