There are a few things that people in the UK do without question. One is say something like “weheeyyy” when someone drops something or falls over (why?). Another is to immediately sit on some grass drinking cans for hours with a top off at the mere hint of it being over 15 degrees. And another is to treat “Hey Jude” by The Beatles as the unofficial national anthem.
Some people don't even like The Beatles, or Paul McCartney and his piano. Plenty of people don't like “Hey Jude” as a song (who is Jude and why are we saying “hey”?). Regardless, upon hearing those opening piano chords, it is your responsibility, as a person in the UK, to stop what you're doing, sling your arm around the person nearest to you and slur “Hey Jude, don't make it bad / Take a sad sooong and make it better” in the most sentimental and off-key way possible and then go “Na-na-na na, na-na-na na” for a good 12 minutes or so, with your whole chest, maybe while fist-pumping.
On the Saturday night at Glastonbury, during McCartney's headline set, people were whispering “When do you think he’ll play ‘Hey Jude’?” until towards the end, when people were literally screaming “PLAY ‘HEY JUDE’… NOW!” The man, who has just turned 80 by the way, obliged around midnight. At which point thousands upon thousands of people clutched their warm paper cups of lager and released their troubles via the medium of collective balladry.
So please behold: the pure elation and emotion that is people's faces when McCartney closed his headline set with the most misty-eyed and well-known song to exist from 1968 onwards.