I recall seeing this mystery film in the 80s, possibly on PBS, perhaps on MYSTERY! Then again it may have been a rental tape.
At any rate, it involved a murder investigation being conducted at a British boys school. In the only scene I can remember, one of the detectives went into an attic storage space, only to have the door pulled shut, locking him in while a fire was set down below, filling the room with smoke.
I seem to recall one of the investigators resembling a young Terence Stamp, but I’ve been through his filmography with a fine tooth comb and it doesn’t seem to have been him.
Young Sherlock Holmes (1985)?
No, there was no fantasy element at all, just a more or less present day police investigation. Thanks, though.
Could it be A Murder Of Quality? https://m.imdb.com/title/tt0102485/?ref_=fn_al_tt_0
It’s a good thought, but no. I’m familiar with all the LeCarre stuff, and this definitely wasn’t one of those. Thanks, though! I like that film.
Could it be “Unman, Wittering, and Zigo,” starring David Hemmings?
No, this one was definitely more of a straight ahead mystery, with English police detectives investigating a crime. Thanks, though!