This one started so...comically...that I thought it was going to be a poor entry in the Bulldog Drummond series, with seemingly endless clownish slapstick from Denny & Clive. But it warms up after 20 minutes into an effectively atmospheric thriller, with Drummond yet again in the throes of getting married while adventure takes hold of the situation.
It's surprisingly bloodthirsty, with the baddie killing 3 including an unarmed bobby pointblank - when it happens it's treated by everyone with everyday calmness.
But what really makes it for me are the catacombs/dungeons sets - the film was shot on a shoestring budget (witness the dream sequences) and yet these sets were so convincing I wondered if they were genuine for a while. They must have been re-used but I can't remember seeing them in any other film. Of course the grainy darkness of the print I was watching helped a lot, but it's worth watching for these scenes anyway. But talk about a corny, contrived ending!