It was one of the most audacious murders of the cold war: Bulgarian writer Georgi Markov was waiting for a bus by London’s Waterloo Bridge when a man bumped into him with his umbrella, pushing a tiny, poisoned pellet into his leg. Four days later he was dead. Piccadilly is a true crime documentary that bring new information to light about the likely culprit: The manipulative, chameleonic figure Francesco Gullino, also known as agent Piccadilly, who worked as a spy for the Bulgarian intelligence service for decades.