How is it that Neil Diamond's 1969 song is being sung in sports stadia around the world?
Anyone who watched England beat Denmark last week - and that's about 25 million UK viewers and countless more around the globe - couldn't help be moved by the belting rendition, by both the crowd and the players, of Sweet Caroline. But why that song?
Paul Carr, professor in popular music analysis at the University of South Wales, told the BBC: "It's a song that's got a lot of nostalgic resonance for many of the people who sing it. The big thing is simplicity of the melody, and there's something in the lyrics."
Simple but emotive phrases like "Good times never felt so good" and "Reaching out, touching me, touching you" are coupled with the anticipatory build-up, leading to a rousing chorus. That all makes it a feelgood communal sing-along - especially after more than a year of lockdowns and social distancing.
Diamond has said he actually wrote the love song about his then-wife Marcia, but her name didn't fit the tune. However, he had remembered a magazine photo he had seen of Caroline Kennedy, the daughter of John F Kennedy and Jacqueline Kennedy.
His song reached number four in the US chart and number eight in the UK, and became a staple of Diamond's live shows. But the first hint of its potential as a sporting crowd-pleaser came in the late 1990s when it was played during a Boston Red Sox baseball game for an employee who had named her newborn Caroline.
The Red Sox decided it was good luck, and started playing it every week from 2003. In 2013, the singer pledged all future royalties from the tune to a charity supporting victims of the Boston Marathon bombing.
Win or lose on Sunday night, we can almost certainly expect the song to ring out again around Wembley Stadium.
If you missed it or want to relive the moment, here's a 4 minute BBC edit that shows the momentous scenes after the final whistle, followed by the wonderfully uplifting rendition of Sweet Caroline:
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