A Bulgarian dissident, Markov broadcast on the BBC but in 1978 became a target for assassination after he had attracted the ire of President Todor Zhivkov. On 7 September 1978 Markov was injected with a pellet containing the deadly toxin ricin, dying in a hospital in London four days later. The attack took place on Waterloo Bridge, the assailant using a converted umbrella as a weapon to fire the tiny platinum pellet that was recovered from Markov’s leg only during the postmortem. A subsequent investigation linked the incident to an attempt on the life of a Bulgarian defector, Vladimir Kostov, who had survived an identical attack while he was traveling on the Paris metro 10 days earlier.
According to KGB counterintelligence chief Oleg Kalugin, the pellet gun had been developed in Moscow by the KGB and delivered to the Bulgarians on the direct orders of Vladimir Kryuchkov. Kalugin was later questioned by the police in London concerning his role in Markov’s murder, and the investigation is still continuing with the assistance of the Bulgarian authorities.