Last Christmas, as speculation grew as to who would take over from David Tennant in Doctor Who, a fever seemed to grip the nation. Every paper and magazine made reference to it. Lists were drawn up. Opinions aired. Radio phone-ins collected data on their listeners' favourite Doctor Whos. My husband, the actor David Morrissey, was appearing in the Christmas Special. Could it be him? The episode was teasingly titled The Next Doctor. But he'd promised the powers that be that he would reveal nothing. Children stopped him in the street. Grown-ups accosted him at parties. “I could tell you,” became his stock response, “but then I'd have to kill you.” One small boy burst into tears.

Certainly in 1985 when, as a young actress, I appeared in Doctor Who myself, no one was quite so impressed. Possibly it was because I had a small part as a Cryon, a race of female aliens who existed only in sub-zero temperatures, and my face was covered in a Perspex mask. My voice was also electronically altered, so that even I was hard-pushed to recognise myself among the group of Cryons when I saw it on TV. I was in Attack of the Cybermen, the second story to be filmed with Colin Baker and his American assistant Nicola Bryant, and although it was nice to be in a show the title of which people recognised - I'd just appeared in a devised play about Job in a pub theatre in Chelsea - Doctor Who didn't quite have the status that it has now. Children liked it, almost every adult recognised the spooky, swirling music of the credits, but the fan base was small and cultish. I never imagined then, when I proudly arrived for my first day's filming at the BBC, that 25 years later it would still be part of my life. Royalty cheques still dribble in, the last one was for 79p, and every few months I receive letters from fans. “I really enjoyed your performance as Threst ... please could you send me a signed photograph ...” Occasionally when I'm at a literary festival, ready to read and discuss my latest novel, the person introducing me, having overenthusiastically perused Google, will surprise the audience with this information from my past. “Doctor Who!” An interested gasp will arise from the audience and the planned discussion will quickly be diverted.

But now, thanks to Russell T. Davies, Doctor Who has become mainstream. It was he who convinced the BBC to recommission it, and with, first Chris Eccleston, and then David Tennant, re-created it in a more sophisticated form. It is surely down to this renewed interest that last Saturday, with the release of Attack of the Cybermen on DVD that I found myself at an official Doctor Who event. They'd tracked me down, -- you can run but you can't hide -- and after initial reluctance, I decided I mustn't resist. If nothing else I'd get to see the faces of the people who'd been writing fan letters to a bit-part alien for 25 years.

Arriving in East London, Barking, I assumed I'd be led into a shop full of memorabilia, models of Time Lords, Cybermen helmets, Tardis key rings, posters of Billie Piper. But in fact the local Doctor Who shop had recently closed down. “You can get everything in WHSmith now,” Derek Hambly, the organiser, told me. “The cult element has gone out of it, so we just organise events.”

That day's event was in a working man's club above Iceland in Barking high street. When I arrived, there were already 50 or so men gathered, mostly middle-aged, pale, but all with the contented look of people absorbed by their hobby; sci-fi devotees who were exactly where they most wanted to be. There were a couple of women too, radiating the same enthusiasm.

They knew the drill. They paid their money, were given yellow slips and one by one filed past my seat to collect a signed photo, a signature in the hefty Doctor Who book, and if they could stretch to it, a signed DVD. Most asked for photos of me too, alone, or with them, and they were watched hawkishly by the assistants -- members of Derek's family -- to check that they didn't snap more than once.

Afterwards there was a question-and-answer session. To my relief it wasn't just me sitting on the panel. Another actress from my episode was there, and we reminisced about the claustrophobic conditions under the Cryon masks and wondered whose idea it had been to cast three women and give them long, frilly bubble-wrap moustaches. Hers kept floating into her mouth, wafted by the wind machine and the dry ice. She'd had to beg for it to be trimmed.

I remembered my 2in fingernails and the director's instructions to keep moving my hands, but my most abiding memory was how impossible I found it to get through my one big scene without giggling. I'd been ordered to stay behind for extra rehearsals to check I could manage it at least once. Later the interviewer turned to me. “It would be true to say,” he winked, “that you are in fact married to the Doctor.”

Every eye in the room turned on me, every face filled with longing. I was married to the Doctor? If they couldn't be him, they wanted to be married to the Doctor too!

“Well, not really ... ” I explained about the Christmas special, and then I had to admit that maybe I had been, just briefly, married to Doctor Who. Maybe I still was! [In fact the job has gone to Matt Smith.]

That night I sat down with my daughter to watch the DVD. “It might be scary,” I warned her as the music began to swirl, but very quickly she delivered her verdict. “It's not scary because nothing looks real. The cybermen are just men dressed up in silver suits. Doctor Who looks like a clown.”

“Really?” I remembered the rare occasions when I'd seen it as a child, I'd hidden behind the sofa. “Shall I switch it off?”

“No,” she protested, “it's still good. And anyway, I want to see your moustache.”

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