I watched this 1974 Americus Production, “The Beast Must Die” on Svengoolie. This British horror film, made at Shepperton Studios, Shepperton, Middx, England, was directed by Paul Annett (English film and television director). A millionaire big game hunter invites a group of people to spend some time at his English mansion knowing that one of them is a vampire. He plans to find out which one is the beast and hunt them down.
The movie is based on the story “There Shall be no Darkness by James Blish (Science Fiction and Fantasy writer, wrote a series of Star Trek novelizations with his wife, is is credited with the term “gas giant” to refer to large planetary bodies). The narrator for the film is Valentine Dyall (he was the Black Guardian in Doctor Who, Deep Thought in The Hitchhiker’s Guide to the Galaxy, Casino Royale).
Anton Diffring (Circus of Horrors, Fahrenheit 451, Doctor Who: Silver Nemesis),
Charles Gray (You Only Live Twice, Blofeld in Diamonds are Forever, The Rocky Horror Picture Show, Mycroft in The Seven Percent Solution),
Ciaran Madden (best known internationally for her multiple leading Agatha Christie, Shakespeare, and Tom Stoppard roles filmed for television,
Harry Potter and the Half-Blood Prince, Doctor Who: A Christmas Carol, Harry Potter and the Deathly Hallows – Part 1 &2, Kingsman: The Golden Circle) and Tom Chadbon (Juggernaut, Tess, Casino Royale, Game of Thrones.