Stephen Sackur is in Nice to speak to the former Russian oligarch and billionaire businessman Sergei Pugachev. He was once dubbed Putin’s banker, a close confidant who helped Putin reach the top. But their relationship soured. Pugachev was accused of massive financial crimes; he renounced his Russian citizenship and now lives with armed guards in the south of France. What does his extraordinary story tell us of Putin’s strengths and weaknesses?