British movie/series set in late 1600/1700s/early 1800s - man with black hat

Hi all,

I recall seeing a British production that was shown on American TV in the early 1980s. The production seems to be MAYBE was set in the late 1600s or 1700s...(but also could have been early 19th century/Dickensian).

The movie/series was shot on film (lots of low lighting, candlelight), on location at least for exteriors, was a period piece and I can only recall a man wearing a black hat/dark glasses and there seemed to be some intrigue around maybe crime/body snatching or related. There were some kids in the production and they seemed to be very much like street urchins.

I suspect this was probably a one series BBC-style production. I cannot recall any of the actors or any other details but it's been driving me nuts for 40 years.