This oldy came to mind reading of Camerons visit to Brazil.
At the height of the Iraqi War, Donald Runsfeld briefed the President,George W Bush, with the news that three Brazilian soldiers had been killed in Iraq.
To eveyones amazement all the colour drained fom Bushes face, he then collapsed over his desk, head in hands visibly shaken, almost whimpering. Finally he composed himself and asked Rumsfeld, " Bob, just how many is a brazillion?"