If you played a musical instrument as a child, the chances are you learnt “When the Saints Go Marching In”. The melody is a gift for beginners: cheery, repetitive, largely stepwise. The words, meanwhile, are easy to adapt, making it a favourite for group singalongs. You’ll hear it passed around campfires or belted from football terraces. Indeed, few songs in the Western world are better known – a fact recognised by the Songwriters Hall of Fame in 2006 when it was awarded “Towering Song” status for having “influenced our culture in a unique way over many years”. But, unlike “Happy Birthday to You”, “Over the Rainbow” or any of the other 19 songs recognised in this way, “The Saints” has no standard version and no known composer – just a rich history of transformation.