* EnforcedMethodActing: Ian Hendry, who plays Eric, was in line for the title role and never forgave Caine for taking it. The onscreen hatred you see is very real.
* PlayingAgainstType: Michael Caine, usually the LoveableRogue (at the time), is the SociopathicHero.
* RealitySubtext: The tension between Carter and Eric Paice (Ian Hendry) was assisted by the fact that Carter was originally going to be played by Ian Hendry until Michael Caine was hired, much to Hendry's resentment.
** One of the most dating parts of the film is the porn movie: it is on film, silent, in black-and-white, and Carter watches it on a clattering projector. [=VHS=] reached the UK in 1978, less than ten years after the film's release.
** Names go in and out of fashion. Names like Doreen and Glenda were reasonable names for young women to have in 1970, but 40 years on, they are old lady names.