Bjorn: I am reminded of Abba every day
7 April 2014 Last updated at 18:15 BST
It is 40 years since Abba won the Eurovision Song Contest in Brighton - a victory that started their meteoric rise to super group status with millions of fans around the globe.
When the four-piece stepped on to the stage accompanied by a man dressed as Napoleon to deliver their country's entry for the competition, they were virtually unknown.
The audience at the 1,700-seat Brighton Dome on 6 April, 1974, had no idea how huge the Swedish group, who performed Waterloo, would become. Most of them were concentrating on the UK entry - Olivia Newton John with her song Long Live Love.
40 years on they are still the second most successful band ever, after The Beatles, selling 375 million records.
The group were one of the most photographed bands in history and to mark 40 years since their Eurovision win, they have released a book of unseen photos.
Bjorn Ulvaeus and Frida Lyngstad spoke to BBC News about Eurovision and what they put their success down to.