British police insisted they had no specific reasons to believe they would find hazardous materials at Boris Berezovsky's house, but given the regularity with which Russian dissidents die under mysterious circumstances, they clearly were not taking any chances. Berezovsky had lived in self-imposed exile since settling in Britain more than 12 years ago and becoming one of the loudest opposition voices against Russian President Vladimir Putin and the Kremlin. The man, once considered one of Russia's richest, had at one time been a part of the Kremlin's inner circle - and had been pivotal in Putin's rise to power. Al Jazeera's Rory Challands reports.