Prime Minister Sir Keir Starmer is facing the first explicit threat of a leadership challenge from one of his MPs - but just how much of a threat does it pose to him? The former minister Catherine West's interview with Radio 4's PM programme immediately raised eyebrows around Westminster. Plenty of Labour MPs from across the party have told us they didn't see it coming. "What the hell is going on?" said one figure on the Left. "Crikey," said another. Equally succinctly, a former frontbencher