This was actually on the Talking Pictures channel in the UK (they’ve actually been showing more and more from the seventies as of late), and to be blunt, I had never heard of it before. But in the summary, it said that the great Christopher Lee was in it (though it’s a small part). Need I say more

This and the fact that it was a 70s movie and based in England, made it a required watch. I’ve always had a more than nostalgic feel for this type of genre; that is gritty, real, basic, and contains a “look what London & the UK looked like in the 1970s”, before digital happened.

Subsequently, I’ve learned that it was one of the first “slasher” types of movie, and when combined with the London Underground and the smaller budget, it is highly effective at what it does.
The film stars Donald Pleasence, who would later star in Halloween .
Enjoy the styles, dialogue and feel from the 70s.
CB