The Lumineers’ record sales would be impressive for any genre in any era. For a 21st century folk rock band, they verge on the remarkable. The Denver band’s self-titled 2012 debut has racked up more than three million sales worldwide to date, shifting 418,418 copies in the UK and propelling them from Hoxton Square Bar & Kitchen to the 10,400-capacity Alexandra Palace in little over a year. 

Following the million-selling success of their monster sing-along breakthrough track Ho Hey, which ...