Narration by ... John Houseman?

The very brief narration at the film's beginning goes, "Dartmoor Prison. Isolated from the outside world by walls of granite."

This sounds exactly like the voice of John Houseman of The Paper Chase (1973) fame. It has his distinctive timbre, inflection, and cadence - at least to my ear. Houseman was already well-known at the time, producing, writing, and editing for many studios, including Universal where Dressed to Kill (1946) was produced. The problem is I can't find any reliable source of information that the voice is Houseman's in order to place him in the cast.

I'm certain I'm not the first person to notice this.