“Never waste a good crisis” is what the Obama crowd always say. Watching David Cameron saying that anyone interested in public service should consider applying to become a Tory parliamentary candidate made me think that the expenses row may be a Godsend for him. After all, what he needs to do to complete the modernisation of the party is to get rid of all those reactionary toffs with their moated piles and Mayfair flats — and until now they have proved rather difficult to eject. But now…?