We should remind ourselves that Europe has brought down two or maybe even three prime ministers. Margaret Thatcher was ousted by an attack from the fanatically pro-Europe Michael Heseltine. During the leadership contest which he then daringly launched, Tory MPs declined to give him the vote of confidence he wanted. His days were numbered.John Major lost all authority in his fight with the Maastricht Treaty rebels — the ‘bastards’ as he called them. Before this pair, there was Ted Heath. The 1974 election that ended his disastrous prime ministership certainly owed something to Harold Wilson’s wily promise to renegotiate EU membership terms and call a referendum. Whether it was the key issue behind his defeat is something the psephologists still argue about but the answer is: ‘Yes, very probably.’ This is an astonishing list of scalps. David Cameron, if he does not look out, will be victim No 4.