Blue Monday had inauspicious beginnings: depending on which of New Order's myth-puncturing stories you believe, it was written either to test out a new drum machine or in order to have a piece of music that would in effect play itself live, allowing the encore-shy band to leave the stage early. But whatever the reason, it was a defining point in their career. For some time they had been inching away from Joy Division's gloomy shadow towards a new sound, influenced by early 80s Italian electronic disco, but this was the moment when everything clicked: a song without a chorus, on which the closest thing to a recognisable hook was the juddering drum machine pattern, which proved commercially unstoppable. Not even a flatly dreadful Top of the Pops performance could stop it becoming the biggest-selling 12-inch single of all time. But it symbolised something more than New Order escaping their past. Myth held the sleeves cost so much to manufacture that their label Factory lost money on every copy sold: in that tale was seen proof that some indie labels really did value art over commerce.
Alexis Petridis is the Guardian's head rock and pop critic