My understanding of the word billion is that it is the number that is represented as a one followed by nine zeros in American, but the number that is represented as a one followed by twelve naughts in English; a thousand million in the USA, but a million million on this side of the pond.
So when Mr Cameron and Mr Osborne talk about a billion pounds are they:
A) Genuinely talking about a billion pounds sterling?
B) Using the American usage out of ignorance of English usage?
C) Using the American usage in order to exaggerate the reality of the UK's financial problems?
D) Bastardising the English language for some other reason?