If you've heard of this, you'll probably already have a fair idea what it's about. If not, to summarise: an ageing TV actor has to return to the location of his '80s detective show, in character, to assist police in finding a delusional murderer who thinks his character, the Mindhorn of the title, is real.
The trim dynamic actor of thirty years ago is now a forgotten, pot-bellied loser who needs a fake tan and a wig to emulate his previous self.
It's not much of a spoiler to say the actor/Mindhorn gets much more involved than planned, finding himself immersed in a conspiracy of murder, cover-ups, political corruption (on a local council level) and marital infidelity.
It's very silly and much funnier than we was expecting. Probably the biggest asset to the film is how it is very British, in a good way. Set on the Isle of Wright, with its modest locations and provincial status, the film doesn't try and pander to wider audiences, the fictional show's narrowness of vision, and the film playing it straight-faced make it all the more enjoyable.