The critics of Vladimir Putin – Russia's Prime Minister and former KGB agent – have a strange habit of being found shot or stabbed or poisoned. This week, I met a man who is half-expecting an assassin's bullet – here, in London. He is not alone. Ahmed Zakayev – a big, broad man with a grey beard and grief-soaked eyes – says: "I remember holding a press conference near here with my dear friends Alexander Litvinenko and Anna Politkovskaya. Now they are murdered and I am the only one left. But I have no right to sit in a hole and shake. I have to speak."