On October 13, 54 CE, Roman emperor, Claudius, died from poisoning under mysterious circumstances. During this time of the Roman Empire, an emperor dying of old age in bed would have been the only mystery. It was normal for the emperors to be poisoned, stabbed to death, or to take their own lives before anyone else could kill them to seize power. So, in effect, Claudius died from natural causes. Mysteriously poisoned by his fourth wife Agrippina so his grand-nephew Nero could succeed him.
There was also a very good PBS mini-series based on his life, starring Derek Jacobi as Claudius. Share Twisted-History to learn more. Not about the mini-series, just more in general.