Siouxsie Sioux and Steven Severin met at a Roxy Music concert in September 1975, at a time when glam rock had faded and there was nothing new coming through with which they could identify. From February 1976, Siouxsie, Severin and some friends began to follow an unsigned band, the Sex Pistols. Journalist Caroline Coon dubbed them the "Bromley Contingent", as most of them came from the Bromley region of South London, a label Severin came to despise. "There was no such thing, it was just a bunch of people drawn together by the way they felt and they looked". They were all inspired by the Sex Pistols and their uncompromising attitude. When they learned that one of the bands scheduled to play the 100 Club Punk Festival, organised by Sex Pistols manager Malcolm McLaren, were pulling out from the bill at the last minute, Siouxsie suggested that she and Severin play, even though they had no band name or additional members. Two days later, the pair appeared at the festival held in London on 20 September 1976. With two borrowed musicians at their side, Marco Pirroni on guitar and John Simon Ritchie (already commonly known as Sid Vicious) on drums, their set consisted of a 20-minute improvisation based on "The Lord's Prayer".
While the band intended to split up after the gig, they were asked to play again. Two months later, Siouxsie and Severin recruited drummer Kenny Morris and guitarist Peter Fenton. After playing several gigs in early 1977, the band realised that Fenton did not fit in because he was "a real rock guitarist". John McKay finally took his place in July