Though Troughton would eagerly make more reappearances in multi-Doctor stories, this would be the last time Hartnell appeared as the First Doctor, and his only multi-Doctor outing. He had been suffering from arteriosclerosis and his condition was beginning to heavily deteriorate from the terminal sickness. His wife advised against a physically demanding role out of concern for his failing health. For this reason, Hartnell's role in the story was limited to recorded pieces from a chair in Ealing Television Film Studios. He was given cue cards to assist him, after a history of misreading his lines due to the effects his disease had on his memory. Nearing the end, William Hartnell succumbed to his illness only two years later.