Isn't there sort of unwritten Glasto rule where if you become big off the back of a contrived primetime "talent" show then Glasto just isn't for you? I remember James Arthur banging on about "Glasto snobbery" a few years back because he was butt hurt he has never asked to play despite his chart success. I'm pretty sure a good chunk of Harry's set is One Direction hits and although they were internationally huge, it's still X Factor sh*te. Maybe there's exceptions who have played in previous years who I can't think of?