The murder of Boris Nemtsov, Russia's most high-profile and charismatic opposition leader has sent shockwaves across Russia, and drawn condemnation from across the world.
Barack Obama, David Cameron, Angela Merkel and Garry Kasparov were among those who called for a through investigation into the killing of one of Vladimir Putin's key rivals - a death the Russia President has said he will investigate personally.
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But who was Boris Nemtsov? These are 19 things you need to know:
