In March 1970, Hopkin represented the United Kingdom in the 1970 Eurovision Song Contest, achieving second place with "Knock, Knock Who's There?" Although she gave a confident performance and sang in a crystal-clear voice, and despite being the pre-contest favourite, Hopkin lost to "All Kinds of Everything", performed by Irish singer Dana. Produced by Mickie Most, "Knock, Knock Who's There?" was released as a single on 23 March 1970 and peaked at number 2 in the UK. It was a worldwide hit, selling over a million copies.