Happiness, loneliness and silliness come together in this startling emotional adventure developed by writer-performers David Earl and Chris Hayward from their 2017 short film of the same name, and directed by Jim Archer. The film is partly about an AI robot called Charles. Charles, a free-thinking robot, is burdened with many things, but an ontological crisis isn’t one of them.

Earl himself plays Brian, a nerdy middle-aged bloke living alone in a Welsh cottage that he has all too clearly inherited from his late parents. He talks directly to a figure behind the camera, with a strange, self-aware nervous giggle.

Poor Brian has recently come through some tactfully unspecified emotional crisis and has now thrown himself into his hobby: inventing things. He has developed an egg-belt – that is, a belt for keeping eggs in – and a pine-cone bag, a bag with pine-cones glued to it, which is not an invention so much as a design concept. He has attempted a flying bicycle, but it is only when foraging for raw materials from fly-tipped rubbish, and discovering a glove and mannequin’s head, that he is inspired to attempt his masterpiece: a robot.

Like a mixture of Caractacus Potts and Victor Frankenstein, Brian works day and night in his shed on his creation, which is to give him friendship and intimacy for the first time in his life, and brings him together with a woman in the village who has a crush on him, Hazel (Louise Brealey). Brian does his best to keep Charles in a state of ET-type secrecy and disguise, but his creature catches the eye of a horrible neighbourhood bully called Eddie (Jamie Michie). And devotees of folk horror will be unnerved to hear that Eddie hosts a big annual bonfire.

Charles is a fascinating figure, the laughs coming from the tiny head on the giant body and the robotic voice with its sing-song falling-tone mannerisms, nicked from Stephen Hawking. Charles looks a bit like an aged and un-aristocratised version of Ray Alan’s sinister ventriloquist dummy Lord Charles.

It isn’t easy to develop a sketch-length idea into a feature film and not easy to pivot from ironic comedy into dark Straw Dogs-style menace, and then into a sweet-natured happy ending. But Earl, Hayward and Archer have managed it. It’s the bromance of the year.