Two arrests have been made over the murder of Russian opposition politician Boris Nemtsov, a crime for which multiple theories still exist. Was he killed in order to cow opposition to President Vladimir Putin at a time of mounting economic problems? Or because he opposed Russia’s alleged covert war in Ukraine Or was he shot in full view of the Kremlin in an attempt to discredit Russian leaders or even intimidate them, or incite a rebellion against them? Perhaps it was an opportunistic attack by someone harbouring a grudge. Here are some of the theories circulating about who might be behind the killing and why. Some of them stretch the imagination, possibly in an attempt to obscure more obvious truth.