Soon after I turned 11, the best thing in my life happened: I won a caption competition run by Target Books, and my prize was a trip to BBC Television Centre in London to meet Doctor Who. I wore Jesus sandals. (Even Jesus couldn't really rock a Jesus sandal.) Also: brown shorts and, for some insane reason, on this, the best day of my life, a T-shirt of my dad's, also brown, advertising guitar strings. Because it was 1983, I had a very bad, Scottish version of Princess Diana's layered hair, only with a long piece hanging down the back, like a rat's tail.

It was pitch dark in the bowels of Television Centre, and busy-looking people were putting tin foil over mattresses to turn them into "space mattresses". A rotund man with a beard was making expansive gestures in a tiny, lit-up control room high above the sound stage. Best of all, I was standing next to the Doctor – the real, live Doctor, with celery in his lapel and everything – who was standing next to the actual Tardis.

I peered feverishly into the Tardis through the gloom. "Ah," said Peter Davison, who was charming, particularly to my mother, who had gone a bit giggly. He followed my gaze into the balsa wood box. "I wouldn't go in there, son. You'll find it very disappointing."

What did I think was going to happen? That I was going to get whisked away to be the new companion? (Yes. That's exactly what I thought would happen. I was a very young 11.) Or that maybe, at the very least, the Doctor – who knew everything – would be able to guess my gender? I did.

It was hard being a young female Doctor Who fan. For a long time, I thought I was the only girl in the world who dreamed about the extraordinary thrill of vanishing into space. Now, any girl who won that competition would get kudos; in 1983, I got a nasty teasing. I loved the Doctor's bolshy companion Tegan (Janet Fielding), and demure Nyssa (Sarah Sutton), too – even if she did get out of the more frightening adventures by fainting. But Bonnie Langford and I simply could not get along. And then there followed the great hiatus when the show went off air.

I waited along with everybody else, watching UK Gold repeats at odd times of day, admiring the extraordinary fortitude of Doctor Who Magazine, which somehow stayed in business for the 16 years the show was suspended. Then, in 2005, a flicker of excitement began to build. Seriously? Christopher Eccleston? He was hot off a drama called The Second Coming, written by Russell T Davies, which displayed his extraordinary skill≈at parachuting the oddest of things into the most believable of settings. There was a point, 15 minutes into that first episode, when New Who's success became inevitable. Even now, you can say these lines to a Who fan anywhere in the world and they will respond immediately, like Friends fans doing the four claps from the theme tune:

Rose: If you're an alien, why do you sound like you come from the north?

The Doctor: Lots of planets have a north.

The slightly childish skew of the first couple of episodes (aliens doing farts!) was cool, but then came a triple whammy of such sophistication that any sense this was just an overexcited kiddie show with good CGI was sent packing: Steven Moffat's The Empty Child episode, featuring Billie Piper flying in a union flag T-shirt, an invisible spaceship parked at Big Ben, and a horrifying, gas-masked child zombie asking if you were his mummy; Paul Cornell's Father's Day, a heartbreaking meditation on love and loss; and the chilling Dalek episode, with Billie shouting, "Hahaha, it can't get up stairs!" – whereupon the Dalek simply levitates and massacres an entire platoon. In Billie Piper's Rose, we had a normal girl who was brave, conflicted and instantly recognisable.

We all know what happened next: David "Bar-sa-LEUN-ah" Tennant turned up. Now, up until then it had been fairly clear that the Doctor couldn't possibly be attracted to humans. (And Time Lords aren't born anyway, they're woven - yes, yes, off to the comments section with you to dispute this.) Tom Baker summed it up perfectly in Douglas Adams's wonderful episode City Of Death, with the line "You're a beautiful woman... probably."

When David Tennant came along, there was a new problem: he and Rose had chemistry: ridiculous, undeniable chemistry. You could tell the makers didn't particularly want it to happen any more than the protagonists did: but there they were, falling in love, as was the mother of pretty much every child in the country watching the show, adding to the ever-rising ratings. (I won't name names, but in 2007 at least four of my romantic novelist friends published books featuring slender, dark-eyed heroes with minds like quicksilver.) And then there was the marvellous Donna (Catherine Tate), huffing down corridors in her Per Una and reminding you what fun a girl can have in the Doctor's universe.

Last year I wrote a Doctor Who book, and the publishers were a bit wary when I approached them, worried I would up the snogs. We decided to publish the book as JT Colgan (I don't have a middle name; the T stands for Tardis), but the fans don't care a bit (they're a pretty smart bunch), so we're reclaiming the Jenny: next time round, I'm Jenny T Colgan.

Can girls write the Doctor? Of course we can: Naomi Alderman's Doctor Who book is terrific, and AL Kennedy's forthcoming Tom Baker novella is sensational. Should we write more of the show? Well, I think the producers should do what they've always done: pick the best writers they can think of. Am I outnumbered at panel events? Yes. Does it bother me? Nope. The chances of there being a female Doctor in my lifetime are, I feel, approaching 100%.

Watching the show as a woman may be a different experience. This may or may not have anything to do with gender, but it took me a lot longer to get over Amy Pond losing her baby than it took Amy Pond. In fact, had I been Amy Pond (and yes, I wish that, too), I would have marched up to the first weeping angel I came across, closed my eyes, and begged it to hurl me back in time: to where I could grab my little girl back into my arms, and make my own getaway.

This may also be a female thing, but I am still sending several begging letters a month to my delightful and long-suffering editor at BBC books, pitching a book set against the background of Martha and Mickey's inevitable and messy divorce. Likewise, excited as I am to see DT and Rose back for the 50th, I've already mentally decorated their house and named their numerous redheaded children.*

Being a fan these days is a very different thing: you can watch every episode as often as you like, and freeze frame your favourite bits, which may or may not include David Tennant leaning his head sideways on a wall. But the loveliest part is getting to meet other female fans at conventions and online; I've met other people who remember what it was like to feel little, and powerless, and who dreamed of exploring infinite worlds in the blink of an eye – and still get home in time for egg and chips.

Oh, and a few years ago I read an interview with Tennant, and he was asked if he'd always been a Doctor Who fan. Yes, of course, he said. In fact, when he was 11, he had entered a Target Books caption competition to meet the Doctor. He didn't win.

*Adric, Katarina and Sarah-Jane

• Jenny Colgan's Doctor Who: Dark Horizon is published in paperback by BBC Books at £7.99. To order a copy for £6.39, go to guardianbookshop.co.uk. She is currently working on a follow-up, Doctor Who: Into The Nowhere.