ABBA's Björn Ulvaeus surprised fans as he attended Mamma Mia's 25th West End anniversary and the band's 50th on Saturday. ABBA's Björn Ulvaeus surprised fans as he attended Mamma Mia's 25th West End anniversary on Saturday The Swedish musician looked smart in a teal blazer with matching trousers and a black T-shirt for the event as he joined Jane Moore …
