It would be just like the Clash to intentionally hide what just might be their most poppy and infectious track ever from public view, but that's not why 'Train in Vain' wasn't originally mentioned on the tracklisting for their 1979 masterpiece 'London Calling.'

Instead, the song was simply hastily written and recorded in a 48-hour span near the end of the sessions for that album, and originally intended to be given away free with a British music magazine. When that deal fell through, the group added the track to the album, even though the cover art had already been printed.