William Hartnell in the Three Doctors
By: +David Herron; Date: Sat Jun 23 2018 17:00:00 GMT-0700 (PDT)
During Jon Pertwee's time as Doctor, they wanted to have the first multi-Doctor story which came to be The Three Doctors. Unfortunately William Hartnell was physically unable to deal with the stress of performing an entire series of episodes. They came up with the idea to have Hartnell appear for a few minutes each episode, via a video screen, reading a few lines.