One of the biggest bands in pop music have reunited, more than 40 years since their last performance.The four members of ABBA gathered together to receive knighthoods in Sweden's King Carl XVI Gustaf. Agnetha Faltskog, Bjorn Ulvaeus, Benny Andersson and Anni-Frid Lyngstad became Commander of the First Class of the order for "very outstanding efforts in Swedish and international music life".