Paranoiac
1963

In the early 60s, it appeared that Hammer could do very little wrong. They were still riding high on the success of their Dracula and Frankenstein films, and were producing a wide range of other genres too.
One of their most successful was the "They're trying to drive me MAD!" thrillers written by Jimmy Sangster, of which Paranoiac is the best example.
To give any of the plot away would spoil the film for you, dear reader. Suffice to say there's a character in it who some of the other members of the cast are trying to drive MAD!
Good old Oliver Reed (looking like a scary, musclebound Robbie Williams) is the star turn as the deranged (everyone's slightly deranged in this one) young heir to a fortune who's more than a bit put out when he supposedly dead older brother turns up out of nowhere.
Of course, before we can suss out who's the Paranoiac (a made up word, if ever I heard one) there's a whole heap of twists and turns - not to mention a shit-you-up, chuck your tea all over the cat, shout out "shit" at the top of your voice to no-one in particular, moment about three quarters of the way in. What is it about black and white movies that they always get me going more than their Technicolor brethren?
With these thrillers, Hammer were aiming to out-Hitchcock Hitchcock, and with Paranoiac they nearly succeeded. It's possibly their most scary film. And when you tie that in with the general head-scratching "what the hell's going on now?" approach that these thrillers had, you've got a film that'll at least hold the interest.

Paranoiac (1963)
Director: Freddie Francis Writer(s): Jimmy Sangster, Josephine Tey (novel Brat Farrar)
Cast: Janette Scott - Eleanor Ashby, Oliver Reed - Simon Ashby, Sheila Burrell - Harriet, Maurice Denham - John Kossett, Alexander Davion - Tony, Liliane Brousse - Françoise, Harold Lang - RAF Type, Arnold Diamond, John Bonney - Keith Kossett, John Stuart - Williams, Sydney Bromley - Tramp, Laurie Leigh - 1st woman, Marianne Stone - 2nd woman, Colin Tapley - Vicar, Jack Taylor - Sailor