On Jan. 1, 1977, Joe Strummer took center stage at London’s burgeoning punk rock refuge, the Roxy. As if presciently ordaining himself the harbinger of what was in store for the pivotal year, “1977” was scrawled boldly across the frontman’s tattered white collared shirt as he and his fellow Clash comrades stormed through two back-to-back sets, officiating both the launch of the Roxy as a cultural touchstone and the explosion of the U.K. punk movement as a whole.

After an unsuccessful run as an “alternative" nightclub called Chaguaramas, situated in the Covent Garden neighborhood of London, Andrew Czezowski, then-manager of the Damned and Generation X, took ownership of the building. Initially intended as a place for his client acts to rehearse, he along with partners Barry Jones and Susan Carrington soon pawned a number of their personal possessions, furnished the venue, and stocked the bar, reviving the haunt as the Roxy, hoping to do for London’s punk scene what CBGB did for New York.

The music scene within which the Clash had been slowly ingratiating themselves had begun years before the fabled New Year's gig, but it had been trammeled by censorship, infamy, and poor luck. 1976’s Anarchy Tour, wherein the band, accompanied by Johnny Thunders’ Heartbreakers, supported the Sex Pistols on a string of ill-fated dates, the majority of booked appearances had been canceled due the pressure of local political interests or the volume of protest demonstrators. By the time the tour had dissolved in scandal on Christmas Eve, as retold in Nick Crossley’s Networks of Sound, Style and Subversion: The Punk and Post-Punk Worlds of Manchester, London, Liverpool and Sheffield, 1975-80, almost two-thirds of the 20-odd scheduled dates were killed before a note had been played.

The ill-repute earned by the failed Anarchy Tour mostly plagued the Sex Pistols, however, as they headlined the bill while the Clash occupied the most modest slot, below that of the Heartbreakers. With hardly a reputation visible enough to damage, they were best positioned to recover. De facto Sex Pistols documentarian Julian Temple, whose forgotten footage of the Roxy evening (embedded above) was finally unearthed for the 2015 BBC Four documentary, The Clash: New Year's Day '77, told the network at the time of the release, “The Clash weren't known at all outside a very small circle, but I thought they were an incredible band in the making.”

Armed with a sharpened assortment of politically militant punk rock anthems-in-waiting, most of which would eventually appear on their eponymous debut three months following the Roxy gala, Temple recorded subterranean Clash rehearsals, capturing now-familiar numbers in their embryonic form. Where the Sex Pistols expressed their subversive proclivities with sneering confrontation and a manic public image (and in a sense, establishing the “punker” archetype), the Clash honed more melodic and informed song structures and envisaged a more focused and clear-cut ideological vision.

But it wasn’t the Clash’s brand of more organized and presentable subversion that was originally slated to break in the newly rebranded Roxy. As Marcus Gray put it, in his book The Clash: Return of the Last Gang in Town, “The Clash agreed to headline the 1 January 1977 Roxy opening night, thus beginning the new year with a highly symbolic act: stepping on the Sex Pistols’ shoes.”

The suggestion is only slightly hyperbolic, as it was Pistols manager Malcolm McLaren, in his characteristically mercurial fashion, who pulled his clients out of the gig at the last minute as a result of the fallout following the Pistols' infamous appearance on the Today show. Still, the symbolism of the turn of events is not exaggerated. The memorably turbulent, not to mention capacity-defying, performance was the first of a series of overtures that would propel the Clash past the perpetually embattled Sex Pistols in the U.K. punk rock hierarchy.

The Roxy’s reign, on the other hand, would be tragically short-lived: it shuttered its doors in April 1978, little over a year after its grand opening. But not before cementing its legacy by cycling through the gambit of prominent English punk acts of the era, from street-punk squatters like Crass and Slaughter and the Dogs to art-school post-punks Wire and Siouxsie and the Banshees. Despite the brevity of the Roxy’s run, the bands it hosted and movement it helped launch proved bigger and more lastingly influential than the Clash and their contemporaries could have predicted.

50 Rock Facts You May Not Know