LONDON — In the annals of television interviews, a drawing-room chat with a 91-year-old woman, watching home movies and offering occasional droll remarks, would not seem like edgy stuff.

But that all changes when the woman is Queen Elizabeth II.

“The Coronation,” a documentary on the 1953 ceremony to air on the BBC here and on the Smithsonian Channel in the United States on Sunday, marks a thaw for the queen, who has never agreed to an interview on camera. (The exchange, in deference to palace sensitivities, is being described as a “conversation.”)

It represents the culmination of 20 years of petitions to the palace, backdoor lobbying with protective courtiers, leveraging of family relationships dating back centuries and a television culture that has, with the popular cable series “The Crown,” yielded the queen’s inner life to the domain of fiction.