Ricin the attack on Georgi Markov another Bulgarian defector, Vladimir Kostov, survived a similar attack. Kostov was standing on an escalator of the Paris metro when he felt a sting in his lower back above the belt of his trousers. He developed a fever, but recovered. After Markov's death the wound on Kostov's back was examined and a ricin-laced pellet identical to the one used against Markov was removed. Several terrorists and terrorist groups have experimented with ricin and caused several incidents of the poisons being mailed to U.S. politicians. For example, on May 29, 2013 two anonymous letters sent to
London Buses route 7 from Wormwood Scrubs were renumbered 7A. This situation remained until 3 October 1934, when the newly constituted London Passenger Transport Board instituted its own numbering system. Route 7 continued with an extension to Kew Green until 22 August 1946, when the 7A was revived from Acton to London Bridge. Route 7 was withdrawn on 19 August 1958. From 14 October 1959, the old route 7A had its suffix removed, becoming plain 7. The service ran between Acton tram depot and London Bridge station via East Acton, Ladbroke Grove, Paddington station, Edgware Road, Marble Arch, Oxford Street, Holborn station and Bank