I was there at the beginning. That's what I remember – watching the first episode twice, because of public demand and that pesky business with the grassy knoll. And I remember the dreadful pepperpots appearing, and the moment that the first companions left – that strange grandchild and those remarkable and rare teachers who took everything in their stride, including time travel and a police box bigger on the inside – and we realised that in the so‑far surprisingly safe world of Doctor Who things could change. They were barely mentioned again, as far as I remember. And the series marched on. Until the great defining moment, the decision that would propel the series on for 50 years – the change of the main character, the first regeneration. It's easy to forget now how groundbreaking that moment was. Our hero dies – and the series continues, a different lead with different tics but somehow still the same man.

I was 18 when Patrick Troughton took over from William Hartnell and other things – mad, confusing, exciting things like drink, girls, Daleks – no wait, not those – were happening. But I still watched it when I could, and some of those moments are still with me. It's funny that way, Doctor Who, it's been such a part of the DNA of Britain for so many years now that even if you didn't watch it religiously, you probably know more about it than you think. Daleks, Cybermen, bigger on the inside – everyone knows what you're talking about. And it was always a safe option for Saturday afternoon tea with the family. Doctors came and went, but for 26 years it was part of this country's shared heritage and memory. Anybody my age or younger has been informed by it, moulded by it, at least to some degree. For so many during those years it was their first introduction to science fiction, and its influence is far-reaching. Generations of authors, screenwriters, actors, dreamers found their escape in the wonky corridors and Styrofoam monsters of this enduring institution.

And then it went away. I had watched a few episodes with my daughter, but it wasn't for me anymore, and at times was obviously suffering from lack of budget and care from the BBC. I was saddened for the kids who would grow up without that comforting madness in their lives, telling them that you could be good and clever and save the day and you didn't have to brandish a gun to achieve those things. But the wheel turns and all things shall come to pass (after an entertaining but ridiculously American stutter with Paul McGann) and there it was, back on Saturday nights, the odd bloke with the phone box that travels in time, having adventures and saving the day.

And I watched it, and it was great. It reminded me of my childhood, which is always a nice thing at my age. But, at last, we had a Doctor who could act – and I mean could really act. Oh, it wasn't science fiction any more (had it ever really been?) there was too much waving of screwdrivers and flying of spaceships looking like the Titanic and "the day has been saved because". Not because of anything that made sense, quite often, just because. That's not SF, not really – that's make-it-up-as-you-go-along. But that's OK, as the show has never really pretended to be much more than this. And the recent actors have been wonderful, drawing that line back to the grumpy old man who kicked it all off 50 years ago. And the Daleks are still scary, which isn't something you can say about many half-century-old alien designs. I love the fact that there are children out there who are learning that life can take you anywhere, and anything can happen, and it can be fantastic. But also that sometimes, life takes away as well. The hero can fail, or die, and we don't all have a magical hand‑wavey way to regenerate ourselves. It's an important lesson.