After a steady trickle of albums, there'll be a Best Of ... along soon, but in the interim, something more fortuitous has fallen into Bragg's lap. He has been charged by Woody Guthrie's daughter with the job of breathing new life into the songs of the legendary American protest singer, whose grainy ballads told the tale of the dust-storm devastation of Thirties' Oklahoma, and the families who fled to California, the promised land - only to wind up destitute in migrant workers' camps.
The dustbowl blues are the works we know best, but Guthrie, who left the midwest for Texas, LA and eventually New York, wrote more than a thousand songs. In 1954 he was hospitalised with the hereditary wasting disease Huntington's chorea and, though he scribbled on until his death in 1967, the illness saw him excluded from the folk scene he had kick-started.
He had recorded only a fraction of his own songs when his daughter Nora, who runs the Woody Guthrie archive on New York's West 57th Street, found a stash of lyrics. She set about finding someone who could give them melodies, and her choice was a troubadour from the badlands of Essex.
The route was circuitous. In 1991, Bragg wrote a song around the title of an erotic Guthrie drawing, You Woke Up My Neighbourhood: the following year, he played it at a concert to mark the 80th anniversary of Woody's birth. In 1996, he was there for Guthrie's induction into the Rock and Roll Hall of Fame in Cleveland. "I've been asked," he said, "to do something in the spirit of Woody Guthrie. So I'm gonna go and have a piss from the balcony and steal all the cutlery backstage."
"Here is someone who knows what dad was really like," thought Nora, sick of Guthrie's status as holy cultural icon.
Bragg took some persuading, but not too much. "Initially, I didn't think I was the person to take on his legacy - but when I realised how much stuff there was, I thought, `It's not like I'm working with the last few scraps, and if I screw it up, there'll still be a lot left.' "
In addition, the idea wasn't to make a tribute album but to turn out a collaboration, with Guthrie's lyrics, Bragg and post-grunge rockers Wilco writing tunes and singing vocals. The result, Mermaid Avenue (named after Guthrie's Coney Island family home), is cool, rocky and fresh. The songs deal with love, lust and footloose dreamers, and you'd never know they were 50 years old.
But then Guthrie is not an historical relic, as Bragg points out. He opens a folder full of copies of the original lyrics, scrawled in Guthrie's increasingly scrambled handwriting. "Look at this," he says, thrusting the bible into my hands. "See what this one's called?" The song is My Flying Saucer. It seems strange that Woody was space age ...
"Never mind that," says Bragg. "See the note, top left-hand corner? What does it say?"
"Supersonic boogie," I mumble, thinking that Bragg would make a fine schoolteacher.
"Instead of this little guy in the dust bowl, like some character in The Grapes of Wrath, you realise he's living in New York City at the most exciting time. This stuff shows he was a living, breathing man."
A bit of a womanising, boozing, wild man, by all accounts.
"He was a punk rocker!" Bragg hoots. "And when I saw `supersonic boogie' - what he wanted, though he couldn't move - it was like Woody was whispering in my earhole saying, `Go on, I dare you to take these sacred texts and do what I would've done with them.' "
It seems odd that Nora asked an Englishman to interpret an American legend - but it was sensibility, not accent, she was worried about. Guthrie and Bragg play on the same team, politically speaking - Guthrie's guitar bore the celebrated legend, "This machine kills fascists" - and Bragg is keen to point out that half the songs Guthrie grew up with, sung to him by his grandmother, were English folk ballads. "We forget that the white Anglo-Saxon Protestant population of the States is an immigrant culture, and Woody's people come from the same place my people come from. I don't mean Dagenham. But you know that song on the album, "Unwelcome Guest"? You'd think it's about a Jesse James-type outlaw, but his horse is called Black Bess. Now, whose horse was called Black Bess? So that, to me, became a highwayman ballad. When I wrote the tune, I thought it should sound like "Streets of Laredo", and the tune of that is from an English ballad, "St James Infirmary"."
Other songs from the collection range from an ode to Joe DiMaggio to the Sputnik launch in 1957. How painful was it for Bragg, and Wilco's Jeff Tweedy, to sift through words written in the last stages of Guthrie's illness? "Nora won't have him seen as a victim. Me and Tweedy came across this song which is just verse, verse, verse, going, `Oh God, Oh God, Oh God' and we imagined him drowning in this terrible disease. But Nora said it may have been revelation - `Oh God! Oh God!' - or may have been his mantra. I've learnt a lot about positivity from her."
Does Bragg feel he ever did more in the Eighties than preach to the converted? "Well, first, it's about entertainment. And then, was I true to what I believed in? And if I feel that I was, that's all I can do. I can't go out and look for signs of how my songs changed the world - it's pointless, frankly." Woody Guthrie would probably grin, light a cigarette, and say the same.
The album `Mermaid Avenue' is released by EastWest today. The book `Woody Guthrie: A Life' by Joe Klein (Faber & Faber) has just been reprinted with a foreword by Billy Bragg.