This caused a regeneration witnessed by Sarah Jane and the Brigadier. In the 1981 story Logopolis, in the act of saving the universe, the Fourth Doctor fell from the gantry of a huge radio telescope.

However, this is the first and only time in which the circumstances of the Doctor's regeneration at the start of a series remain unexplained. This is only the second time in which the Doctor ...

Regeneration is the "secret sauce" of Doctor ... in large part because of the length of his tenure. The Fourth Doctor, ...

However, as well as the addition of the Fourth Doctor’s face ... is given the task of looking after the Doctor during his recovery from his regeneration. At the close of the story, Harry ...