Graham Kibble-White steps back in time with Elisabeth Sladen...

On a dark October night in 1976, 12 million people tuned in to Doctor Who, unaware their hearts were about to be broken.

Having received the summons to return to his home planet of Gallifrey, the Doctor (then played by Tom Baker) made a quick stop at the slightly less sci-fi location of Hillview Road, South Croydon.

It was here he unceremoniously dropped off his long-suffering assistant, Sarah Jane Smith, who reluctantly disembarked the Tardis after three years of memorable adventures at the time-traveller's side.

"Don't forget me," she whimpered, as she made her exit.

For anyone who grew up watching the series during those years, Sarah, as played by Elisabeth Sladen, has indeed remained unforgettable.

And while Billie Piper may be mightily impressive as current sidekick Rose, those of us of a certain age still reckon the spunky, screaming "girl reporter" is the one to beat.

However, while we may not have forgotten her, it seems the Doctor had. Until now.

This Saturday, she returns to the series for an emotional but spiky reunion with her former best friend.

"I had a call from my agent that [Doctor Who's executive producer and lead writer] Russell T Davies and [producer] Phil Collinson would like to take me to lunch and talk about the show," explains Elisabeth, who, at 58, incredibly looks hardly a year older than when she last stepped out of the Tardis.

"I thought they might be asking me to come back for just one small jokey scene, in a little homage to the old programme," she continues.

"I was actually thinking, 'How can I turn this down? My agent will kill me', because I wouldn't have wanted to have done anything like that.

"I'm very protective of Sarah, I really am. So I felt I'd just have to explain that I'd rather let the character stand as she was.

"But we opened a bottle of wine and Russell and Phil told me all about it, and it was then that I realised they were talking about bringing her back for a full episode.

"So I felt very comfortable and supported, otherwise I wouldn't have done it.

"I did have reservations as to how much responsibility was on the character, and the last thing I wanted was for people who'd been so loyal to the show over all these years to say, 'My gosh, she wouldn't be like this! What is she doing?'. That would be the worst thing.

"But what came out of the script was very much what I had in mind for her. There were a couple of things we had a bit of a disagreement about, but that was fine.

"I suppose I just thought it was a really good opportunity, and also a challenge to see if we could get it to work."

Despite the fact it's been three decades since she starred in the show, Elisabeth laughs that "it was surprisingly, embarrassingly not odd" to be back in Doctor Who.

"I just thought, 'Oh, there's the Tardis, there's the Doctor'. Both of them fitted, far too snugly."

Current Doctor and confirmed fan of the old series, David Tennant, has gone on record as saying he found it almost overwhelming to work with Elisabeth, having spent his growing-up years watching her on television.

"I spied him at the read through and he spied me," she reveals. "We circled each other a bit, and then I thought, 'Well, how ridiculous'. So I said hello, and I got the biggest hug of my life.

"I mean, he's absolutely delighted with the role and what he's doing with it now."

Having worked alongside classic Doctors Jon Pertwee and Tom Baker, she's well qualified to give her opinion on the current incarnation.

"Any actor playing the Doctor not only has to be good, he has to have charisma as well, which Jon and Tom had in spades. And I think David's got it too. He has the ability to remember the Doctor is an alien and he's not always going to react in the way you think he is."

She's also impressed with Billie Piper, although she says the actress didn't seem particularly keen to quiz her on her own experiences.

"I don't think that was the brief she needed," she explains. "I don't think Billie's someone who looks back, and it wasn't necessary other than in the script."

As for Elisabeth, although she left Doctor Who in the 1970s, Sarah Jane has never really left her.

She first returned to the role for a one-shot spin-off, K-9 And Company, in 1981 - and indeed, that robotic mutt will be back too.

Since then, she's appeared as Sarah in numerous other Doctor Who video projects, and more recently in a series of audio adventures available from Big Finish Productions, in which she takes centre stage. The latest of these, Sarah Jane Smith: Dreamland, was released earlier this month.

"I wasn't sure they'd be a great success without the Doctor," she confesses, "because I thought, 'If you go around with a guy with two hearts and then you're dumped back on Earth, well, who can you talk to?'.

"It's so lovely that she's endured. I have to say I kind of aspire to some of the qualities she has. I like her."