The brazen assassination of Mahmoud al-Mabhouh has thrown the spotlight on one of Israel’s most powerful but shadowy figures, Meir Dagan, the current Mossad chief, who yesterday faced calls for his resignation. There is a piece of folklore often repeated about him: when he was appointed in 2002, Ariel Sharon, then the Prime Minister, ordered him to run the Israeli spy agency “with a knife between its teeth”. Eight years on, Mr Dagan appears to have followed his orders to the letter. The killing in Dubai of one of the top men in Hamas is only the most recent in...