Abba duo Benny and Bjorn on Mamma Mia! success
13 April 2014 Last updated at 19:47 BST
Abba's Benny Andersson and Bjorn Ulvaeus were among the famous faces who gathered at the Royal Opera House in central London on Sunday for the Olivier Awards.
The duo were invited to perform at the event alongside the London cast of Mamma Mia! - to celebrate the musical's 15 years in the West End.
The spoke to the BBC's Lizo Mzimba about the show and why they thought it had been such a success.