1666

1666 was a year of particular interest to several incarnations of the Doctor, mostly because of the Great Fire of London and the then-rampant bubonic plague.

In late August, the Fifth Doctor, Adric, Nyssa, and Tegan arrived in London on the trail of a Terileptil invasion. A few days later, on 2nd September, the Doctor accidentally started the Great Fire of London. (DW: The Visitation)

Shortly thereafter, George, Helen, Ida and Alan Mortimer were rescued from the Great Fire by the First Doctor. (DWAN: Doctor Who and the Invasion from Space)

Around this time, the Fourth Doctor and Sarah Jane Smith were also in the vicinity of greater London. They landed the TARDIS in a bubonic plague-infested area. Sarah contracted the plague, while the Doctor tried to warn the locals — some of whom were Republicans and some of whom were loyal to Charles II — to the spread of the oncoming Great Fire. He managed to get the two groups to work together against the approaching fire, then returned to the TARDIS with the ailing Sarah in time to give her some useful antibiotics. However, some of the antibiotics were stolen by one of the locals. The theft threatened to destroy the delicate fabric of the Web of Time. (ST: The Republican's Story)