Russian opposition leader Alexei Navalny was killed using a poison developed from a dart frog toxin, the UK and European allies have said. Two years on from the death of Navalny at a Siberian penal colony, Britain and its allies have blamed the Kremlin following analysis of material samples found on his body. There is no innocent explanation for the toxin, called epibatidine, being found in samples taken from Navalny's body, the UK Foreign Office said. UK Foreign Secretary Yvette Cooper