I first saw this film as a teenager. It was a Saturday night and I was at home, bored, but not wanting to go to bed. My parents, of course, were already in bed. Back in those (pre-historic) times, the number of TV channels available in Britain was severely limited, but I "flicked through" all four of them, somewhat listlessly. I'm guessing it was either BBC2 or Channel 4 that were announcing their "late night film" and it sounded promising, if not exactly exciting, so I decided to give it a go.
And I was soon hooked! Laurence Olivier and Michael Caine are fantastic. You can tell it's a stage play in origin because it's pretty static, but there's action all the same, and the dialogue is sparkling. I can't really tell you much about the plot without giving things away, but the starting point is that Caine is the lover of Olivier's wife and Olivier invites him to his house for a discussion. After that, well... you'll just have to watch it!
There was a remake, with Caine playing Olivier's part and Jude Law playing Caine's part, but I haven't seen it. According to the reviews, it isn't as good.
After that first viewing, it soon became one of my favourite films. The next time I saw that it was on, I videoed it and was then able to watch it whenever I wanted. Since then, I've probably seen it about 5 or 6 times, it just never gets old (even though it IS old - 1972!).
I get the impression it's not a particularly well-known film. I've often mentioned it to people, and most never seem to have heard of it, which is a terrible shame. If you haven't seen it, and if you like intelligent dialogue and a plot with more twists and turns than a Cornish country road, get hold of this and watch it! I'm sure you won't be disappointed. I'm kind of tempted to watch the remake, just to see what it's like...