I found other Hammer films excruciating boring
this one is also - great actors, great basic story, great scenes - however something is not right. as if someone intentionally ruins and sabotage the film in the name of hammer - so we have boring dialogues, important scenes speeded or slowed down, then more of boring dialogues
This one's, admittedly, not very compelling, but there are plenty of good or great Hammer films, like "The Curse of the Mummy's Tomb" (1964), "The Two Faces of Dr. Jekyll" (1961), "Frankenstein Created Woman" (1967), "Frankenstein Must Be Destroyed "(1969), "Captain Kronos -- Vampire Hunter" (1974), "One Million Years B.C." (1966), "Five Million Years to Earth" (1967), "These are the Damned" (1962), "The Brides of Dracula" (1960) and many more.
They're relatively low-budget and products of their era, but the better ones have quality writing with the corresponding interesting characters, not to mention lush colors, effective ambiance and a jaw-dropping woman or three. To appreciate 'em you have to acclimate to a different time and mode of storytelling; don't expect an explosion every five minutes or any CGI.