Leo X, born Giovanni di Lorenzo de Medici, was Pope in the early 16th century.
He was a collector of arts. He was rumoured not to be interested in women. Perhaps, to cover up this fact, he offered Vicki Pallister a place of his consort.
The First Doctor, Steven Taylor and Vicki got entangled in the plot of his brother Guiliano de Medici, conspiring with Niccolo Machiavelli against him. After the Doctor showed Leo the inside of the TARDIS and gave Machiavelli great manuscript to read, the Pope published the manuscript bringing eternal shame on Machiavelli's name and demoted his brother from the Captain General of Florence to a cardinal. (AUDIO: The Ravelli Conspiracy)
Behind the scenes
Tom Baker played Leo X in the 1974 film Luther.