It began with one man's attempts to de-clutter and has culminated in Evanton in Easter Ross becoming the setting for an unexpected rock music reunion that comes to fruition in London tonight.

When Iain Clark contacted a Reading-based record dealer earlier this year, he was looking to offload the 600-700 vinyl albums that he had accumulated and no longer played. Among them were one or two items that he felt might be worth a bob or two but he didn't want to get involved in individual sales or internet auctions.

The dealer, Damian Jones of Pop Classics, looked at the list Clark had sent and asked how he came to have five albums by the 1970s prog rock band Cressida, whose two albums for the Vertigo label have been known to fetch up to £1000 on eBay. "I was their drummer," replied Clark.

Before Clark knew what was happening, Jones and his business partner, Rob Henson had jumped in Jones's car and had driven to Evanton to meet him. It turned out that they were big fans of Cressida from way back and had always wondered what had happened to the various band members. Meeting Clark was a life-long ambition.

"They asked if there were any unreleased tapes of the band anywhere and I said, I don't think so," says Clark. "But then I started looking into cardboard boxes that hadn't been opened in years and asking around the rest of the band, who were living as far away as Los Angeles, and we found some 3¼-inch tapes that were in a very fragile state and had to be restored and digitised. Once that was done, lo and behold we had enough music for an album, which was bizarre because none of the band remembered making so many demos."

At this point Record Collector, the UK's first monthly music magazine and the bible for vinyl junkies worldwide, became interested. The magazine's rare record club wanted to put out a limited edition vinyl album of the unreleased tracks. By this time contact had well and truly been resumed between the estranged band members and a reunion gig was mooted. Would the magic that had brought Cressida a whole new following through their original albums being reissued on CD fall back into place?

In September, four of the original group – guitarist John Heyworth having passed away in 2010 – convened in Clark's house in Evanton, with local guitarist Roger Niven taking Heyworth's place. After an awkward 30 minutes or so, things began to gel and after a week spent re-familiarising themselves with their old material and a commitment to go off and work on their parts individually, they decided that a reunion gig was possible. A venue, the Underworld in Camden, was found and a date set. Tickets started selling to Cressida fans from Tokyo to Rio de Janeiro. So this past week, Evanton has been host to the final preparations.

Why Evanton? Despite having great- grandparents from Inverness and the Mull of Kintyre and a Scottish mother, Clark is very much a North Londoner, although he's lived in Easter Ross for close to 25 years now and regards it as home. As a youngster he became fascinated by the drums through listening to the Shadows and Gene Vincent & the Blue Caps and progressed from hitting an upturned bin with two bits of wood to, first, a rickety snare drum then the kit he bought with his first term's grant at teacher training college.

His early bands included one in Cheltenham, The Ramrods, whose guitarist, one Brian Jones, had left for London a few months before and formed the Rolling Stones. After playing semi-professionally while at college, when Clark followed Jones back to London to take up a teaching job, he soon decided to go full-time into music.

After the first professional band he'd joined split up after six weeks, Clark auditioned successfully for a band being built around the guitarist Danny Kirwan, who was poached almost immediately thereafter by Fleetwood Mac. Then in late 1968 he answered an advertisement in Melody Maker, auditioned and was invited to join Charge. With a new name, Cressida, they became one of the first bands to sign with Phillips Records' specialist underground label, Vertigo.

Cressida's eponymously-named first album was released on Friday, February 13, 1970 along with the first album by Black Sabbath and Rod Stewart's An Old Raincoat Will Never Let You Down. They toured with Black Sabbath, kept busy on the college and club circuit and became the first British band to play in Czechoslovakia as well as playing all across Europe. By the time they began work on their second album, Asylum, however, tensions had crept into the band and as the gigs began to dry up, they split before the album was released in early 1971. Which probably didn't hinder its progress, aided significantly by Vertigo's legendary and much-sought-after early "swirl" label, towards collectability.

Clark went on to play with Uriah Heep, appearing on the heavy rock band's Look at Yourself album, and continued working in music until he looked up his friend and fellow Cressida alumnus, singer Angus Cullen, who had moved to Easter Ross.

"I came up for a couple of holidays, played a bit of music and decided that there was such a great community spirit here that I had to move permanently. I was also ready to leave London as I'd had enough of big city living," he says. He went on to form a Youth Training Scheme-led charity that got young people in the area involved in the performing arts and became a pioneer in connecting rural areas in the Highlands and Islands through computers and early use of broadband, eventually forming his own IT company based in Dingwall.

All through these nearly 25 years he kept playing drums in his spare time. He had a band with David Foster, a fellow music-business escapee in the Highlands who had worked with Yes, played in an early version of Highland folk rockers Wolfstone, formed a now long-running blues band with the aforementioned Roger Niven, The Twisted Blues Band, and joined Niven in the Inverness-based Ecuadorian singer Coca Tenorio's salsa-influenced band.

"The million-dollar question everyone now asks is whether the Cressida reunion is going to lead to other things," says Clark. "To be honest, I've had my share of schlepping around in vans and band buses and I'm not sure I want to get back into intense touring. But we've been invited to appear at a prog rock festival in the States next October and that sounds good. We'll have to wait and see. There's certainly interest, amazing interest from around the world in the Camden gig, so I won't rule anything out and apart from anything else, getting back together after all this time has been great fun. The rehearsals have been going really well."

Cressida play Underworld in Camden, London tonight.