Georgi Markov, a dissident writer, “was assassinated on a London street via a micro-engineered pellet containing ricin, fired into his leg from an umbrella wielded by someone associated with the Bulgarian Secret Service. It has been speculated that they asked the KGB for help.[2]” Wikipedia. Minuscule amount of ricin kill the victim in around four days.
The museum illustrated many vicious assassinations or attempts during our times. Agents included VX (Novichok nerve gas) used against Segei and Yullia Skripal (both of who survived) and polonium 210 against Alexander Litvinenko.