I know, I know: David Cameron, the guy who overcame his privileged and cosseted upbringing, is the one who’s actually going to be living at that address. But the man who put Cameron at Number Ten Downing is a Frenchman named Baudoin Prot, the chief executive officer of BNP Paribas, a huge multinational banking firm — and Cameron and the Tories had better do as he says, or he can break them just as he made them.