Death Line (Gary Sherman, 1972)

Not what I expected, this. The title, the premise (and certainly some of the original posters) suggest a violent claustrophobic horror with people getting picked off by cannibals living in the London Underground. But it's something very different - an attempt to create a properly tragic Gothic monster, rather in the Frankenstein tradition. I'm not sure that the above-ground plot (weary detectives, MI5 cover-ups) and the below-ground horrors mesh very satisfactorily - though perhaps there would be a way of watching it that made this very much the point - but it's an intriguingly valiant effort. And Donald Pleasence is absolutely terrific throughout (particularly entertaining when just about avoiding swearing, and in some splendidly sarcastic rapid shifts of facial expression).