This not-half-bad take on the Frankenstein legend plays like a black comedy, with Bates playing the doctor as an arrogant rich kid and womanizer. O'Mara is his maid, lover and ultimately blackmailer.
It is a Hammer Film, but it wasn't officially part of the Hammer Frankenstein series, starring Cushing as the doc. If Cushing's Frankenstein was evil sometimes (as in "The Curse of Frankenstein") he was often portrayed as something of a good guy, particularly in "Frankenstein Created Woman," possibly the best Hammer Film of them all.
Bates does a good job playing the doctor as a deceptive, ruthless, sadistic backstabber. The monster he ultimately creates is used to dispatch his enemies. The bald creature is played by David Prowse, who seven years later would play Darth Vader in "Star Wars."
It's an odd sort of horror fan who would like this movie, which certainly isn't up to the standards set by the '50s and '60s Hammer films and lacks the gore and sex of later ones. But it's a fairly enjoyable black comedy, although the script leaves much to be desired. There's almost no plot and the film's ending is the weakest Hammer has ever delivered. Still, catch it if you can. It was in print on video briefly in the 1980s.
Bates also starred in the early '70s Hammer film, "Doctor Jeckyll and Sister Hyde."