MAY 27, 1967, Golders Green, London. A fledgling four-piece group plays its first-ever concert. It is an auspicious date, as music writer Rob Young would much later observe, even in such a key year for rock music. Hendrix's Are You Experienced? had just been released, and Sgt Pepper was on its way.

January 24, 2017 (next Tuesday, in other words): That same group, still going strong, kicks off its 50th anniversary year with a Celtic Connections show at Glasgow's Old Fruitmarket.

Over that half-century, Fairport Convention have weathered countless line-up changes, but the current one - Simon Nicol, Dave Pegg, Chris Leslie, Ric Sanders and Gerry Conway - is the longest-running one in the band's history. Then, of course, there's the distinctive music, the template for which was set by that glorious opening run of albums: Fairport Convention, What We Did On Our Holidays, Unhalfbricking, Liege & Lief, Full House. Liege & Lief, in 1969, was a radical landmark and managed to reinvent folk-rock. Joe Boyd, who produced it, wrote in 2002 that it remains a "groundbreaking work of genuine originality and bravery."

Fairport, who are releasing a new album, 50:50@50, to mark the anniversary, are also responsible for the long-running Cropredy Festival, in Oxfordshire. This August's line-up includes The Divine Comedy, Dougie MacLean and Marillion, as well as ex-Fairport members Ashley Hutchings, Richard Thompson, Judy Dyble, Iain Matthews, Dave Mattacks and Chris Leslie. (Sandy Denny, such a bewitching presence on ...Holidays, Unhalfbricking and Liege & Lief, died, sadly, in 1978).

It's to the band's lasting credit that they have never rested complacently on their laurels but have kept their sound fresh, as evidenced by their most recent studio album, Myths and Heroes.

"In terms of commercial success, of course, our crop of laurels is fairly meagre," acknowledges co-founder Simon Nicol when that is put to him. "For a band that has been around for 50 years there are not too many mega-platinum albums. But I take your point. That's why we are where we are, why we're still active, and touring as a band. It's not about, 'Okay, we had a big hit album in whenever-it-was, and now we're going to go out and play it until we get completely sick of it, and pretend we're still 18 years of age'.

"We do refresh the repertoire regularly and we keep the pot stirred. We obviously don't neglect our past, we're very proud of it, but we're not enslaved to it."

The new album is divided between live recordings and studio numbers. "I thought that was the right approach. I'm aware there's a lot of interest in the band because we're reached this milestone, so I think a number of people will come back and re-discover us. I though it would be a good idea to have the touring and performing side of the band shown off on some of these tracks.

"We have some choice performances of mainly up-tempo songs, which shows what the band is good at doing onstage. The album also illustrates what new songs are coming through and, if you want to use those possibly as a way of saying which direction the band is going in, you could do that. I'm pleased with the balance on the record," he adds, "and I'm more than pleased to have had half-a-century of gigging, and I still can't wait to get back in the van."

Fairport Convention indeed have an unquenchable appetite for gigging, for meeting their fans. "That's the work ethic," he says. "It's not a hardship. We have that in common: we all like the countdown to going on stage. It's what we do. It's all about the performance on the night." As for the fan-bonding, he says that all the bands he's been in have eschewed the notion of mystique. "There's no kind of divide. You'll see that at Cropredy – there's no backstage bar, and there's only a bar on the field, so punter can meet turn very easily. We've always been that close to our punters, and they're far from shy in telling us what they think. Why shouldn't it be that way? Mystique is all right for some people but it doesn't work for us."

The 20,000 fans who will assemble at Cropredy this year, he adds, come from all over the world and all levels of society.

"And the only thing they have in common is that at some point, Fairport has reached into their lives. That is the reason they're there, and that is something of which I'm hugely proud. It's a fabulous thing. There are no other bands like Fairport, just because it's grown. We just developed this way organically, but at the same time the ethos is about live performance, having fun onstage." He affectionately recalls a "triumphant, just gorgeous, splendid" Celtic Connections show at the Royal Concert Hall two years ago.

The band's storied history also includes a time in the late 1970s when, remarkably, they found themselves without a record deal. But they bounced back even from that and are now as strong as ever.

"We've always been light on our feet," Nicol says. "We've never been sucked into the mainstream of the music business. Obviously, the first 10 years of the band, we were with major labels and all that sort of thing, and they tried their best to turn us into stars. But the planets didn't align, and it didn't happen.

"Now, we're completely autonomous. We do everything ourselves and it works well that way. Maybe this is the reason we have this stability now, because the current line-up is 19 years old, which is a lot longer than the Beatles managed," he laughs.

Are The Rolling Stones their only rivals as an institution in British music? "Yeah," and Nicol laughs again. "But we've done more gigs than the Stones."

Fairport Convention play Glasgow's Old Fruitmarket on Tuesday. Cropredy Festival is August 10-12.

www.fairportconvention.com