Jonathan Haslam is George F. Kennan Professor in the School of Historical Studies at the Institute for Advanced Study in Princeton and Professor of the History of International Relations at the University of Cambridge.
Haslam is possibly the best analyst of Soviet Diplomacy the world has ever been blessed with. Eschewing the usual cold war perspectives that privileged either ideology or Realpolitik (apologia/condemnation for the course history took), he does hard historical research, finding the devil in the details on 'how' and 'why' collective security collapsed in the 1930s.
Regardless, he loses a star for his use of metaphor. See here: 'however much mother Russia attempted to conceal the fact, her revolutionary petticoat kept dropping below the hemline of her ill-fashioned dress.' Etc.