Surrey police are probing the mystery death of a Russian exile who was helping to locate millions of dollars missing from the Russian treasury. City experts claim London is one of the routes for those laundering the proceeds of Russian crime. Britain is also now a destination of choice for many wealthy Russians. But how much do we know about some of those who choose to settle here? Internationally, there's tension between Washington and Moscow over the Magnitsky Act, in which the US introduced new sanctions for Russian officials suspected of corruption, freezing their assets and barring their entry to America. Prominent MPs are arguing for similar measures here. So is Britain too lax in cases where suspicions are raised? Reporter: Julian O'Halloran Producer: David Lewis.