Ukraine, to borrow a phrase from Vladimir Putin, is on the edge of an abyss. The confrontation between the Kiev Government and pro-Russian forces in the east threatens Ukraine's very existence. Who bears responsibility? And who is now calling the shots? HARDtalk speaks to former US Deputy Secretary of State, Strobe Talbott, and Russian opposition leader, Boris Nemtsov. Has the Russian President comprehensively outmanoeuvred his enemies?