The Sixth Doctor:
Loud, boastful and colourful, this extravagant Doctor hid his vulnerability and caring nature behind a boastful mask of alien disinterest. After once again being put on trial by the Time Lords, the Doctor's TARDIS was shot out of the skies by his old enemy the Rani and the subsequent crash triggered a regeneration...
from 'Attack of the Cybermen': The TARDIS is lured to Earth in 1985 where they encounter a group of Cybermen based in London's sewers. The Doctor and Peri are then captured and forced to take the Cybermen in the TARDIS to the Cybermen's home planet Telos. The Cybermen have stolen a time vessel from another race and plan to change history by crashing Halley's Comet into Earth and obliterating it before it can bring about the demise of their original home world, Mondas, in 1986.