London, September 1978: exiled Bulgarian dissident Georgi Markov is murdered in broad daylight on Waterloo Bridge with what appears to be a poison-tipped umbrella. It would become the most infamous unsolved killing of the Cold War.

Many years later, young journalist Ulrik Skotte is approached with explosive new information about a man alleged to be responsible for Markov's death - a spy code-named Piccadilly who worked for the Bulgarian secret service. This meeting launched Skotte into a hunt for the killer lasting more than a quarter of a century, bringing him face to face with eccentric conspiracy theorists, a washed-up former dictator, ageing Danish spooks - and, ultimately, with Agent Piccadilly himself.

Drawing on an incredible cache of original documents, interviews and archive material, The Umbrella Murder provides jaw-dropping answers to questions that have persisted for nearly five decades: who killed Georgi Markov? And who has been protecting the assassin ever since?