Drowning his sorrows at the Rainbow Theatre one night, he met The Clash's guitarist, Mick Jones, who was on the lookout for a replacement drummer. Being part of The Clash meant Headon had to give up his previous existence.
Headon agreed to an audition but didn't bother going; he'd briefly been in Jones' previous band, the London SS, "but they were all long hair and afghans and stuff". Having set off for the audition in casual clothes and with long hair, he returned home dressed in punk gear, his head sporting hacked spikes.
Although already a heavy user, it was to be this event that propelled Headon into taking his heroin addiction to the next level.
"I just stuck needles in my arm, which I'd never done before," he says, explaining how his dismissal became his justification.
"Only a junkie can think: 'I'll show you; I'll fuck myself up even more.'" More than 25 years after the event, however, the drummer has had plenty of time to reflect on where the blame really lies.
When he later moved to London with his new wife Wendy, he was sacked from various drumming jobs for not hitting the drums hard enough, a legacy of these jazz beginnings. – I had to relearn my whole drumming style." He ended up with his hands covered in blood blisters but he'd got the job on a wage of £25 a week.
"The band were getting the hump with me using on stage." He couldn't see what they were getting annoyed about; he had taken drugs with all of them, too.
"I'd think we were getting out of it every night," he recalls.
It was some time before his drumming skills were fully appreciated by The Clash.
His strength and stamina were obvious but his ability to play jazz, soul and funk weren't needed to begin with.
"I loved drumming, so I just thought, 'Right, I'm going to learn reggae now.' That's the way I was – I've got an addictive personality. As the late rock'n'roll legend performed his soundcheck one afternoon, Headon leapt on stage and played Diddley's signature beat.