Who is James Payton? The simple answer is that James Payton is a jobbing actor. You’ve probably seen him in something. His two claims to some kind of fame are blink-and-you’ll-miss-em parts in a couple of franchises: Neville Longbottom’s dad in Harry Potter and the Order of the Phoenix, and Hitler in the first Captain America movie. Payton’s other credits include “geography lecturer” in The Crown and “wasted guy” in a terrible Jonathan Pryce thriller from 2005. The two franchises, however, have opened the door to a nice little side hustle: regional fan conventions where Payton sells signed photos of himself for £10.

The film follows him around the “cons”, where franchise fans queue to get a selfie with Harry Potter’s mate’s dad. Payton wonders how his life got to this? “There was me thinking that one day I’d get nominated for a Bafta for some TV detective thing.” It would be easy to take the mickey. And to be fair, sometimes this documentary comes over like a cross between The Office and The Trip, with a bit of Withnail and I thrown in. (There’s a brilliant moment where a small kid heckles the world’s most half-arsed wrestlers.) But Payton has a very dry sense of humour and he sees the funny side of staying in budget motorway hotels or twiddling his thumbs in an empty community hall.

But going back to the title – I’m not sure the film answers the question in any kind of satisfying manner. I would have liked a bit more prodding from director Oliver Guy-Watkins on the impact of the death of Payton’s dad when he was 12 (which is when he decided to become an actor); his divorce; and his relationship with failure, working in an industry where failure is built in. The film can be a bit of a frustrating watch at times: not so much Who is James Payton? and more Why Should We Care?

• Who Is James Payton? is released on 4 January on digital platforms.