Mickey Smith claimed to be an expert in investigation. (TV: School Reunion) It was described by Giles as "his passion" in life. (HOMEVID: Goo!)
The Fifteenth Doctor, posing as Special Agent Clint Rock of the head office of the Time Hotel, asked hotel employee Trev Simpkins just how the hotel's time portals worked. When Simpkins questioned why he would need to know this, given his being from the head office, he replied that he liked to enter investigations with his mind completely blank, that it allowed him to fit in better. (TV: Joy to the World [+]Steven Moffat, Doctor Who Christmas Special 2024 (BBC One and Disney+, 2024).)