The most disappointing pop performance I’ve ever seen – and in the course of my 15-odd years as a music critic I saw an awful lot – was Kanye West at Glastonbury in 2015. Perhaps he was making some kind of ironic statement on the nature of celebrity and fan expectation: blinding lights all focused on himself; no attempts to engage with the crowd; relentless, mechanical rapping but with most of the amusing samples and catchy hooks removed, the better to punish us all by ordeal with loud, righteous verbiage.