The end of 2006 brought strained relations between Russia and Britain in the wake of the death of a former FSB officer in London by poisoning. On 20 July 2007 UK Prime Minister Gordon Brown expelled "four Russian envoys over Putin's refusal to extradite ex-KGB agent Andrei Lugovoi, wanted in the UK for the murder of fellow former spy Alexander Litvinenko in London." The Russian constitution prohibits the extradition of Russian nationals to third countries. British Foreign Secretary David Miliband said that "this situation is not unique, and other countries have amended their constitutions, for example to give effect to the European Arrest Warrant".