Peter Davison is on a new journey to discover everything he can about the Doctor's Companion. What exactly is a companion's role, how do you actually become a companion, what do they have in common and how have the companions changed over the years?

Peter Davison, the Fifth Doctor, meets the talented people and stars who have helped create the show both past, present and future, and asks 'Who is the Doctor? What makes him tick? What will make the Twelfth Doctor unique?'