[MUSIC] Georgi Markov was a Bulgarian writer, but he had become dissatisfied with the Communist regime in Bulgaria. And in 1971, he had defected to Britain, and he'd started working for the BBC World Service, broadcasting to Bulgaria, in Bulgarian. Saying very unpleasant things about the then Bulgarian regime, and the then communist Bulgarian president. These things did not make him popular back in Sofia. Now, one day, in September 1979, he was in his way to work, and he was standing on Waterloo Bridge, when he felt a sharp pain in one of his legs. And he'd been poked in the leg by an umbrella, held by the man standing next to him. This man mumbled an apology and then disappeared. Well, Markov went on to work but he started to feel unwell. The next day, he was admitted to hospital. And on the following Monday, he died. Well, at the autopsy, the puncture wound from this poke in the leg was found. And the tissue from that part of the leg was sent to Porton Down, the chemical weapons research establishment. And in the tissue, there was a very, very, tiny metallic sphere. SEM-EDX analysis showed that its composition was very unusual. It was an alloy, 90% platinum, the rest was iridium, not the kind of alloy you would come across in normal life. This sphere was hollow, there was a tiny hollow space inside. And they estimated this was big enough for about two milligrams of poison, though there was no detectable poison inside it anymore. It was deduced that the poison most likely to have been used inside that metal sphere was a complex polypeptide called ricin. And this can be isolated from the castor oil plant. Rather scarily, the castor oil plant is very, very common. It's quite an attractive plant, and many people might find it growing in their garden. The umbrella was of course, not a real umbrella. It was in fact a pellet gun disguised as an umbrella and probably made by the KGB. This technique had in fact been used the previous year on another Bulgarian dissident called Kostov. The difference was, that whereas Markov died from the ricin poisoning, Kostov had survived. And it's believed this is simply because of the way they were stabbed. The pellet injected into Markov came very close to a blood vessel and therefore the ricin was absorbed very fast, reaching a high and lethal concentration. The pellet injected into Kostov probably went into muscle tissue, and therefore there was a very slow absorbance of the ricin Into the blood stream. Well, was Markov really murdered by the Bulgarian Secret Services? It seems very likely that this was the case, though many of the records of the Bulgarian Secret Services disappeared with the fall of the communist regime. And many important people in that regime committed suicide, so they can never tell us the truth.