We've seen it happen before, most notably and perhaps most painfully, in the final season of Game of Thrones. Cast your minds back to the utter disappointment when you realised that the vast majority of the plotlines set up in Westeros would amount to nothing, and the Night King would (spoiler) die after doing very little except looking super smug all the time. Having said that, I really don't think the Line of Duty finale was as bad as some people are making it out to be. Did we want the fourth man to be Carmichael or Osborne? Sure. Was it an underwhelming reveal to have the bumbling Buckells revealed as the Keyser Söze of the whole thing? Maybe.