Fan, it's worth remembering, is short for fanatic. But when common or garden fanaticism meets up and shakes hands with disturbed teenage hormones, you just stand back and get out of its way. Caroline Sullivan should know: as a gawky teenager from New Jersey, she spent the latter half of her teenage years in the grips of an obsession that only now, 20 years later, she can claim she is free from. Caroline was a Bay City Rollers fan. And proud of it. It wasn't just a case of buying the records, going to the gigs and cutting the band members' photos out of magazines, though. Between the years 1975 and 1979, she stalked them at airports, pursued them in her car, booked into the same hotel they were using, sat at the next table to them in restaurants, lied her way backstage at their concerts and, perhaps most tragically, affected a dire Scottish accent to inveigle information out of airlines and venue staff.
Now that a sufficient amount of time has passed since her days as a "tartan tart", she has, bravely, regressed herself emotionally, scoured through her old diaries and confronted her past by committing her experiences to print in a rollicking good book called Bye Bye Baby (My Tragic Love Affair with the Bay City Rollers).
For those too young to remember Rollermania, or just pretending to forget, it's enough to know that Eric (scream), Leslie (scream), Woody (scream), Alan (scream) and Derek (scream) were the original of the boy band species. At the height of their dizzying mid-1970s career, they were responsible for female adolescent mass hysteria, they sold more records than David Bowie, had 18 top five hits, had their own TV show, were big in the US and were distinguished by wearing tartan (they were from Edinburgh) in all its naff variations. "I just loved them," says Sullivan, now a feature writer with the Guardian newspaper, "and that's why I chased them around all those years. I really thought that if one of them got the chance to meet me, he would fall in love with me. I was convinced of that."
Sullivan was a bit of an oddity in that when she started following the Rollers, she was the grand old age of 17, a good five years older than their average fan, and she never wore tartan. "I felt that being older was enough to make me stand out and the reason I never wore tartan is that I just knew I was going to end up with one of them and he probably wouldn't want me to look like a fan."
What's odder still is that growing up in suburban New Jersey, Sullivan, as a keen music fan, developed a taste for "real" music, and with her Led Zep records, was no way an identikit teenybopper. Although even now she still can't quite bring herself to be disparaging of their musical attempts, she stresses that the attraction was more because "all of the usual rock bands were full of men, but the Rollers were boys. OK, maybe the music was a bit flimsy in parts but it was merely an adjunct to us chasing them around".
And there were also the friendships - she says she bonded with a group of other (like her) older Rollers fans and they remain the best of friends to this day. "It was a real teenage girl thing," she says, "we did crazy things together like driving for hours upon hours to follow the Rollers around the country."
Such was at her adeptness at what we would now call stalking, that the Rollers and their management team got to know her face and at times when she got right up near them in a hotel or a restaurant, they were shockingly rude to her. "That really didn't matter," she says. "Of course, it was mortifying at the time when a Roller would turn around to you and say something horrible but I couldn't allow it to dampen my ardour. I'd just climb on to the next plane to keep following them around. I absorbed many and varied putdowns and disappointments but I ignored them. You have to remember though, there was a practical reason why I was following them everywhere. I just knew that I was going to meet one of them and he would be seduced by my charms."
Saying that she read Nick Hornby's Fever Pitch before she sat down to write the book, she believes her Roller confessions have as much validity as someone travelling all around the country to sit in the rain watching a (then) boring football team. "I do say in the book that my obsession with the Rollers was probably because I didn't want to grow up, it was a way of postponing adulthood. I grew out of it and got a job and started hanging around with different people. I never kept my Rollers past a secret though, actually I used to brag about it." There is also the matter of her ending up in bed with one of the Rollers, although rather coyly in the book, she won't reveal which one it was. "I didn't want it to be a kiss 'n' tell thing," she says. Apart from being about fandom (especially female fandom), the book also doubles as a tragic insight into a band who fall from favour, with a bump. Late in their career, when they had abandoned the tartan and wholesome image, Caroline finds out that the band are in New Jersey recording a new "rock" album. Using all her old skills, she tracks down where they are staying, rings them up and is astonished when the band (now bereft of fans) pay for her taxi fare to bring her down from New York to have a chat. "Their descent was sad for them and sad for us to watch. It was terrible seeing a band we loved so much brought so low."
Although she had planned to ring the Rollers to help her out with a few odd facts while she was doing the book, she decided against it, figuring that she wanted to tell her own story. She says that her publishing company has sent the members of the band a copy of her book and she hopes that "they will like it, rather than dislike it".
The option for the film rights has just been bought by musician/actress Courtney Love who plans to make her directorial debut with it. "I found out that she too was a Rollers fan growing up - there's a lot more of us than you think," she says.
As for the Rollers now, they've been through some hard times and are the victims of what is generally regarded as one of the biggest pop music swindles of the past three decades. In theory they should have amassed millions of pounds in royalties and merchandising, but they were left virtually penniless by a series of management feuds, internal wranglings and bad investments.
The original line-up have now reformed and are currently in the middle of a "comeback" tour. "They're playing in London next month," says Sullivan. "I can't wait."
Bye Bye Baby by Caroline Sullivan is published by Bloomsbury, price £10.99 in UK