On 17 March 1979, Gloria Gaynor achieved a transatlantic chart- topping double when "I Will Survive" went to No. 1 in the UK. The single remained there for four weeks - Art Garfunkel's "Bright Eyes" knocked it off - and was in the top 30 until mid-May. By the end of the year, it had sold more than seven million copies worldwide; Polydor lost count of subsequent sales, as its message of defiance struck a chord with a generation under siege.

The disco era began with Gloria. In 1974, "Never Can Say Goodbye" was the first disco single to be played on US radio, marking the genre's transition from the gay clubs to the mainstream. Gaynor was then eclipsed by Donna Summer, but "I Will Survive" made the last days of disco a cause for celebration. "It galvanised the Western world," says DJ Paul Gambaccini. "On Broadway, Colony Records played it constantly into the streets over the loud speakers. Even Regine, then the queen of the disco set, recorded a cover."

It then took on a life of its own, becoming a gay anthem in an era of Aids and prejudice, and a feminist anthem for women left by, or leaving, their men. In 1996, Naomi Wolf hailed Gaynor as "one of the most casually influential political figures in the popular culture of the 1970s and 1980s". (In 1997, Gaynor revealed that the song was actually written for her as she recovered from a back injury.) In the Guardian, Suzanne Moore infamously interspersed musings on post-Panorama Diana with the lyrics. Spitting Image had the Queen singing "One Will Survive" in the midst of the Royal meltdown.

Gaynor re-recorded it in 1993; she was by then a born-again Christian, and the line, "It took all the strength I had not to fall apart" was changed to "Only the Lord can give me strength". Though the remix sacrificed the melodrama of the original for something horribly tinny, it still made the UK top 10. Diana Ross has covered it since, and a dragged-up Terence Stamp memorably lip-synched to it in Priscilla. It's the most requested karaoke song in the world.

But it's the original that people still want to hear - at parties, hen nights and Seventies clubs. "YMCA", which was No 1 in January 1979, fills dance floors with those nostalgic merely for ridiculous choreography. "I Will Survive" fills them with people whose every bellowed word carries meaning. "It was and still is an anthem," says Gambaccini. "Every genre that comes and goes in popular music throws up a couple of standards. This is the big disco standard." At London's Starsky and Hutch Seventies clubs, it gets more than 30 requests a night. "The girls love it," says DJ Little Chris. "They can stand around and sing along to it. They don't have to dance to it."

Gaynor told the IoS in 1993 that she never tired of singing it. "It's like telling one of those side-splitting jokes: you get to the punchline, people crack up, you're king for a minute - it's a good feeling, particularly if you're a ham like I am."