'When I say run, run." They're the words of Peter Capaldi in the episode Sleep No More, although it's not the first time that the 12th Doctor has said them, having used the phrase in Series 8's Kill The Moon. However, you have to go back much further to find their original use, as it was 2nd Doctor Patrick Troughton who made it something of a catchphrase, and it has been used by various Doctors, and even appeared in an episode of Sherlock.