To date, the regeneration of the Second Doctor to the Third is the only one that did not involve a death. Instead, he was placed on trial, exiled to Earth and a "change of appearance" was forced upon him, since his face was too well known and identifiable on Earth. While he was initially given a few choices to select from, in true Second Doctor nature he was combative until the very end as he didn't like any of the selections presented to him. Fans had to wait until the next season began to see that Jon Pertwee would step out from the TARDIS, exhausted... and in colour! Speaking of which...