On the sleeve of 1973's Solid Air he's a pretty boy with a head of curls; that boy's gone and in his place is a bruised fighter, balding, bearded and, it becomes clear, equipped with the full complement of internal scars.
After 30 years in the trade Martyn has come some way from the inspired folkie who charmed college kids with his crazy Echoplex guitar, taking them to some kind of sonic dreamtime. Slightly soured by experience, he's harder, tougher, but still vulnerable, and the mix can give his sound an almost ugly ferocity.
Slurring more sludgily with every passing year, Martyn treads a perilous knife-edge between visionary shaman and loose-limbed wino who could be saying anything; and, like all seers, he's a troubled man.
He's also a funny guy, however, full of eccentric, Tommy Cooper-style gags, and it's probably his saving grace. Though no one came expecting an easy night, that was what we got, levitating, undeserving, on seas of sound.
Martyn is playing as part of the Festival of Drifting, but there's little drift to what he delivers. He's lately become a Buddhist, and his recent album, The Church With One Bell, sees him looking outside himself on a batch of covers. There's a philanthropic thrust to it all, and every number, wrapped in his own sensuous, sorrowing blend of blues/jazz/funk, seems tailor-made.
He gave us some of the warmth and desire of the early less cynical years - "Solid Air" and the gorgeous "Couldn't Love You More". Martyn's passion isn't staged but a gruffly beautiful business he can't keep in: "I just like things tender," he says, and it shows.
Though there were times he stumbled last night, it still seemed mad that he never broke through to his rightful big-time success. But he's too edgy, too honest for mainstream consumption, lulling you with his charm then scaring you with his roar. Grizzled hymns from a holy fool.