The inside story of the murder of Alexander Litvinenko in November 2006 by means of the radioactive poison polonium 210, and of the international manhunt that led to the steps of the Kremlin. The Scotland Yard detectives who led the enquiry and the doctors who fought to save Litvinenko's life reveal the political and diplomatic obstacle course they faced in investigating the murder and tell how their quarries left a toxic trail through the heart of London