A constable was a police officer.
The day after John F. Kennedy's assassination, constable Reg Cranfield saw his late father in the mists along Totter's Lane. (PROSE: Shroud of Sorrow)
Groom was a constable in Devil's End. (TV: The Dæmons)
Constable Zreeg was one of the Wrarth Warriors that went to Earth around 1980 in pursuit of Beep the Meep. (COMIC: The Star Beast)
Before she joined Torchwood 3, Gwen Cooper was a constable. (TV: Everything Changes)
After the Space-Time Manipulator sent Jorjie to 1963, he was found by a constable. (TV: The Cambridge Spy)