Interrogation was a process of obtaining information, especially in the course of an investigation, or in response to a crime.

Upon arriving on a parallel earth, the Third Doctor was mistaken for a spy and interrogated. (TV: Inferno)

The Twelfth Doctor said, "The first rule of being interrogated: you are the only irreplaceable person in the room. Make it work for you. If they threaten you with death, show 'em who's boss: die faster." (TV: Heaven Sent)

Police interrogation in the 1970s could sometimes elicit information within 5 minutes, if the suspect was clearly lying. Ann Kelso considered this option in Newstead Abbey, 1852, but the Fourth Doctor talked her down: "You seem to be getting results [already] with your good cop routine." (AUDIO: The Enchantress of Numbers)

On getting permission from Mayor Me to question anyone in London's Trap Street for alien refugees, Clara Oswald suggested she and the Twelfth Doctor split up for their investigation. She would question suspects as "good cop", while the Doctor would act as "bad cop". When the Doctor objected to this arrangement, preferring to be "good cop", Clara reminded him that his appearance was more intimidating. (TV: Face the Raven) "Good cop, bad cop" was an Earth colloquialism. (AUDIO: Neverland)

Behind the scenes[]

In real life, interrogation is mostly used by authorities. They often employ the "good cop, bad cop" routine to get information out of suspects, with one cop being nice and caring, while the second being gruff and threatening.