In Brighton, England, on April 6, 1974, the judges of the 19th Eurovision Song Contest crushed the hopes of tiny Luxembourg by denying that nation in its bid for a historic third straight victory at the pan-European musical event. Those judges did the rest of the world a favor, however, by selecting the Swedish entry as the winner instead. Which is not to say anything against the song “Bye Bye I Love You” as performed by Luxembourg’s Irene Sheer. It’s just that Sweden’s entry was a song called “Waterloo,” performed by a group called ABBA, which went on to become something of a sensation. ABBA’s win at the annual Eurovision Song Contest on this day in 1974 launched the group on its monumental international career, marking the first and still only time that the Eurovision Song Contest crowned a previously unknown winner destined for legitimate superstardom.

The Eurovision Song Contest was originally conceived as a way for the member countries of the European Broadcasting Union to participate in a simultaneous live broadcast—a major technical challenge in 1956. From a one-night event involving only seven participating countries in its first year, the contest has grown into a week-long spectacle involving preliminary rounds of competition among representatives of more than 20 countries in Europe, the Middle East, North Africa and the former Soviet Union. But while the annual contest is now one of the most-watched television events in the world, one thing Eurovision has consistently failed at doing is launching new artists to truly international stardom. The sole, shining exception to this rule is ABBA. (All apologies to 1988 winner Celine Dion, who was already something of a star prior to her Eurovision victory, and to 2006 winner Lordi, probably the finest monster-costumed Finnish metal band of all time, but a band that so far enjoys only a cult following outside of northern Europe.)

The year that ABBA was chosen as Sweden’s Eurovision entry was the second in which contest competitors were allowed to perform in any language they wished. (A national-language restriction was reinstated in 1977 before being abolished in 1999.) This proved to be critical to ABBA’s international success. While the UK judges awarded ABBA zero points toward their winning total on this night in 1974, their English-language “Waterloo” became an instant hit with the British public—the first of nine UK #1 hits for the biggest group ever launched by the Eurovision Song Contest.