Earlier this year I noticed guerrilla-stickered cartoon bubbles around London that posed the question, ‘What would Joe Strummer do?’ They were trailers, it turned out, for a range of hip babygrows. But this mild absurdity exemplified how, almost four years since his death on 22 December 2002, the enigmatic Joe Strummer, spokesman for the punk generation and front man for The Clash, seems to have seeped in everywhere in contemporary culture. In Irvine Welsh’s new novel, The Bedroom Secrets of the Master Chefs, he has a controversial cameo role; the excellent play Meeting Joe Strummer won an award at this year’s Edinburgh festival; director Julien Temple is finishing a film about Joe; a box set of CD singles of The Clash’s original vinyl 45s is released next month; and I’ve finally finished writing his biography, Redemption Song: the Definitive Biography of Joe Strummer.

Why does Joe infiltrate our lives like this? The answer is more complex than death simply having cemented his position. Part of the answer lies in The Clash’s music having proved to be so timeless. Great truths can often be couched in humour, and the group’s often hilarious, satirical lyrics (‘vacuum-cleaner sucks up budgie’, from ‘The Magnificent Seven’ comes readily to mind), as well as the militant prophecies (time has given ‘London’s Calling’’s ‘I live by the river’ line an eerily sinister ring), spring from the internal state of its creators: highly evolved individuals who had truly had a good look at themselves. Partly through their endless Red Guard-like debates at the Rehearsal Rehearsal studios when Joe Strummer, Mick Jones and Paul Simonon first formed as The Clash, they had assiduously endeavoured to keep their feet on the ground and - as one of punk’s dictums insisted - be honest (Joe was ever consumed with angst about not being able to get enough ‘kids’ into gigs for free. At one of his last shows, with The Mescaleros in Japan, he reprimanded a friend who suggested he slip away after signing autographs for a third of the 150 waiting fans. ‘This is my job!’ Joe snapped. He was still there 90 minutes later.).

On a very basic level, the iconic everyman of Joe Strummer is an extremely good idea; in his last three years, playing with his new group The Mescaleros, he seemed on the verge of becoming a kind of Johnny Cash-like elder statesman of British rock’n’roll. And you could still rely on Strummer to speak the truth (even when he was wrong . . .) and crystallise a situation. The ITN evening news item about his death comes to mind: it included footage from the Acton Town Hall show at which Mick Jones had memorably joined Joe onstage for the first time in 19 years, a benefit for the Fire Brigades Union. ‘Give the firemen the money,’ Joe barks as he’s leaving the gig, ‘and the nurses and the teachers too.’ Not surprisingly, Joe loathed Tony Blair and New Labour. ‘He used to wear this t-shirt that said “TLF - the Tony Liberation Front: We’ve got to get rid of Tony Blair”,’ said Lucinda Mellor, his widow. ‘He felt betrayed by this Labour government. When they got in, he was ecstatic, and he really felt betrayed.’ At one point Joe even seriously considered running in the London mayoral elections.

‘There was always something of the loser about Joe,’ the writer Jon Savage suggested to me. ‘That goes back to his squatting days, and you can hear the suffering in his vocals. I think that’s a big part of his appeal.’

Savage is certainly on the right track, but this sense about Joe goes back further than his time in squats. The suicide of his elder brother David in July 1970 irrevocably altered Joe’s life. On the one hand it hardened him. Five years later he spoke about this to his girlfriend Paloma Romano, who became Palmolive when, enraged by Joe dumping her, she founded The Slits: ‘He told me about David - he said that his brother had chosen death and he had chosen life: he had decided to go for it entirely.’ But it also left a void from which Joe never recovered. You can feel that hurt in Joe’s singing, and, sometimes when you were with him, emanating from every atom in his body. When Joe was performing, the audience was entranced by the singer’s explosions of performance art, speaking in tongues, leaping onto speaker cabinets, hurling himself backwards to the stage floor. But there was always a feeling that he was performing almost beyond himself. ‘Everyone loved Joe,’ said Clash manager Bernie Rhodes of the beatnik rocker. ‘But Joe didn’t love himself.’ ‘If you’ve spoken to 250 people,’ said Marcia Finer, the artist wife of Pogues-man Jem Finer, ‘then I would say you’ve met 250 different sides of Joe.’

Strummer’s brother David Mellor had been a member of the National Front - a reaction to this clearly informed the thinking of his younger brother. It comes as no surprise that when The Clash played the Rock Against Racism concert in Hackney’s Victoria Park in April 1978, before 80,000 people, Joe and The Clash were transmogrified into the personification of positive punk - the side that had no truck with the swastika armbands flaunted by Siouxsie or Sid Vicious. It was at that point that Joe became King of Punk - aided by the recent demise of The Sex Pistols - and a serious spokesman for the left.

But the archetypal resonance of Joe and The Clash also lies in the plot-line of the messy demise of the group, occasioned first by the sacking of heroin-addicted drummer Topper Headon in May 1982, and - even more significantly - by the firing of founder Mick Jones in August 1983. As Mick Jones wrote most of the music, this was madness. Although a further Clash line-up toured and recorded, it gradually dawned on Joe that he had allowed himself to be misled. ‘I’ve got a big problem. Mick was right about (Clash manager) Bernie (Rhodes),’ he confided to me in 1985. In the relentless upward drive of The Clash, Strummer had moved at such a pace he hadn’t seen what was really happening, making expedient decisions that turned out to be disasters.

Joe Strummer was now obliged - as he himself later put it - to ‘go into the wilderness’, making an excellent solo album, Earthquake Weather, that was a commercial disaster, and acting in films for directors Alex Cox and Jim Jarmusch. ‘I became close to him during a period when a lot of the time he was really down,’ says Cox. Jarmusch? ‘He had a dark cloud over him. I used to call him Big Chief Thundercloud. But he was still generous and spirited and uplifting to be with.’

Moving out of London, Joe went to live in the West Country. Marrying Lucinda Tait in 1995 seemed to set him on a new course. One wedding present was a pair of tickets to that year’s Glastonbury Festival, which would turn into a life-changing experience for Joe. After taking his first ecstasy, he finally appreciated dance music, and set about writing songs that blended dance and rock’n’roll: one tune, ‘Diggin’ the New’, expressed how he had come to understand a new scene - ‘when you get it, you don’t forget it’.

These compositions mutated into the music played by Joe Strummer and The Mescaleros when they released their first album, Rock Art and the X-Ray Style, in November 1999.

On his annual visits to Glastonbury, Joe would plot up in the backstage area, playing choice sounds non-stop. The centrepiece of his Glastonbury scene was a large campfire, which he personally constructed. Joe’s Glastonbury campfires aimed to reduce the egos of all participants until they could truly communicate. Joe told his friend Julien Temple, the film director, that he believed his legacy might well turn out not to be The Clash but a global campfire scene. ‘Joe totally believed in God,’ said Lucinda. ‘He just hated any form of organised religion. He said to me, “I believe that mankind is inherently good, and that good will always triumph”.’

Redemption Song: the Definitive Biography of Joe Strummer is published on Mon 2 Oct by Harper Collins Entertainment. The 19-disc Clash Singles Box Set is released by SonyBMG on Mon 30 Oct