My religious background – rampant, bigoted Catholicism in Liverpool – prepared me for Doctor Who because we were very strong Christians and you may have noticed there is something slightly shifty about them. I think it must be when you're a Christian you have no privacy. He's there all the time, watching you closely, and you have an angel on your shoulder watching you, so this makes life a bit tough in the bathroom, wondering why doesn't he leave me alone? It's like trying to learn to play the violin under the bedclothes, you can't do it. So believing all this utter nonsense, being brought up with all this bigotry, when I got to Doctor Who, and I realised he could disappear and reappear somewhere else, or that he had this sonic screwdriver to change things, that was all absolutely easy for me. It's been easy ever since, because I have traded on it ever since, because no one would ever give me credit. And even years later when I played Macbeth, I played it like Doctor Who, and people said to me, I had no idea Macbeth was such a nice man, [but I did it] because it would have meant disappointing the audience. I am not interested in actors who are so wonderful that you don't recognise them. I don't see the point of it. When I go to the theatre or to a movie I want to know who the star is, or who the funny man is, or who the beautiful girl is, so I can respond. You were in Doctor Who between 1974 and 1981, perhaps the most successful years of the original Doctor Who series. The image of your Doctor, "all teeth and curls", became iconic, particularly in Australia where the ABC screened the show five nights a week for many years. Was it difficult finding work after Doctor Who? It wasn't difficult to find work because I was in big demand for voice-overs or [to speak at] colleges, and I was being invited everywhere, being flown first class to other countries. And also it means I had to get up early in the morning because so many people were wanting to applaud me, and go, hurrah, you're marvellous. I'd always wanted to be liked, and then I realised what I really wanted was to be adored. When you become a telly star, as in those days, before the video recorder changed everything, that real-time watching and discussing the next day, required us to co-hear, as a population, otherwise you were out of the loop the next day. And so I had to get up early in the morning and go out basking in all this and shocked viewers would just shake their heads and say, it must be marvellous, and I would say, it is.

Although there was a brief interregnum in the 1990s, the show has essentially been in production since 1963. And even while new episodes were not being made, the show's fans never extinguished their torch. Why do you think the show lasted so long? I don't quite know but there's nothing quite like it, is there? And the early audiences seem to be so loyal, that they passed it on. I am still introduced to small children by their fathers and grandfathers now. The BBC has confirmed that a new Doctor, the 12th Doctor, actor Peter Capaldi, will make his debut in the upcoming Christmas special. As a former Doctor, what is your feeling on that? I know him, I have acted with him when I was Sherlock Holmes many years ago, and I think people will think he'll do it like [The Thick of It character] Malcolm Tucker and Malcolm Tucker is a one-note brute. He's marvellous at it, and it was wonderful in [the stage production of] Arsenic and Old Lace, he has a big range and he will give it a lot of authority and mischief.

Do you think when an actor is being considered for the role of the Doctor, some actors are more right for the role than others? Capaldi certainly "feels" right. I don't think anybody knows. It's like Shakespeare, when they're doing Richard II and they say we want someone noble with a fine voice and that doesn't make sense to me because kings are just like the rest of humanity, some of them are wankers and some are not, and just because he's got a nice voice and stands up straight, kings weren't like that, were they? [Capaldi] will come with such a wave of fascination, they will want him to be good, and he will be good. And nobody has ever failed. [A pause.] I find that chastening, by the way. There was for a time persistent speculation that there could be a female Doctor Who? Do you think a woman could take on the role? Well, I don't have any convictions about that, I don't have many convictions anyway. I think it would have been quite nice to have a woman. I think it would have been quite nice to have a man dressed as a woman. I have always wanted to play Lady Bracknell [from The Importance of Being Earnest] myself. Or someone who was very, very obviously gay might break it up. And I don't necessarily see why he has to stay long. If the audience don't like it, kill him off. He doesn't have to be an institution just because I stayed too long. The image of each Doctor has become somewhat iconic – Patrick Troughton's fur coat, Jon Pertwee's velvet smoking jacket, and in your case the hat and scarf. What do you think about the enduring power of that image?

My costume evolved by accident, and [wardrobe supervisor] Jim Acheson, who won an Oscar. [Acheson has actually won three, The Last Emperor (1987), Dangerous Liaisons (1988) and Restoration (1995).] Now it all gets a bit precious, doesn't it? Following me, Peter [Davison] was dressed in some kind of Edwardian cricket gear and then Colin Baker was dressed in that funny way. The scarf was an accident. Jim Acheson bought a load of wool on the taxpayer and went to a woman called Begonia Pope and said, knit me a scarf in these colours. We went round to her little house and we couldn't get in because she'd knitted this scarf which was all over the place because of all of this bloody wool. I laughed, but Jim Acheson said let's keep it that way. And they kept it like that. I quite liked all the silly bits of it. As someone who is uncertain and probably quite close to death, I think the silly things in life amuse me: children, grandchildren, animals, even wives, if they stay. I think about the silly things in real life. You've been on the set of the show twice for "regeneration" scenes, where an actor hands over to the new one: the episode where Jon Pertwee's Doctor turned into you, and the episode where your Doctor turned into Peter Davison's. Are those scenes difficult to shoot? Jon Pertwee didn't really speak to me – he did his scene, they locked off the camera and then he went away and I came in for that shot. The same with Peter, he just came in for that last shot, I really didn't meet him then for a year or two. It just happened that way. I still don't know many of them very well, and I notice, and I don't blame them, but I have a feeling most of them are avoiding me and they're conspiring to make me happy or something. You just don't know with old Doctor Whos. You're so entirely associated with the role now. Do you like the attention the role has brought you? I do. I always enjoy customers. I love it. I love the fans. They're not so young now, my fans, but I do enjoy it – recording for Big Finish [the UK production company that produces a line of Doctor Who audio dramas] or the BBC asking me to do signing sessions with the other actors. I go along and sign pictures of myself. The other day for some charity I had to sign 2500 10-by-eight photos of myself. By the end of the second day I could not look at myself. It was a kind of self-loathing.

You left the role in 1981. Looking back on it now, do you regret leaving when you did? Is there some part of the character, or his world, you wish you'd stayed around to explore a little more? I didn't miss anything because it was spontaneous at the time, it was just me, I just responded to the situation. The other day I was recording an audio drama for Big Finish and they let me put lines in, and just before we [walked into a dangerous situation], I said to Louise Jameson's character Leela, you go first, it might be a trap. That's the kind of silliness in this world, that anything can happen. Louise Jameson understood that, Elisabeth Sladen [who played Sarah Jane Smith] particularly understood that. She liked me from the word go. She came from Liverpool and we got on so well, and unfortunately she stayed so little. And then she died. And then Mary [actress Mary Tamm, who played the companion Romana] died. And the Brigadier [actor Nicholas Courtney] died. Directors are now a bit nervous of me because the word's got out, it is true, that quite a lot of directors, after working with me, have died, unexpectedly. Some of them in frightful circumstances. And that's happened to a few journalists too. The 50th anniversary episode The Day of the Doctor will air on ABC1 on the morning of Sunday, November 24, in simulcast with the UK. It will be repeated at 7:30pm. Doctor Who: An Adventure in Space and Time, the telemovie dramatisation of the creation of the series at the BBC in 1963, will air on ABC1 on Sunday, November 24, at 8:45pm. The ABC's iView platform is streaming 47 hand-picked episodes from the original series on demand, including the show's first serial, 1963's An Unearthly Child, starring the "first" Doctor, William Hartnell.