(Photo credit: Rooners Toy Photography)

I remember the first time I ever saw Doctor Who. My father told me there was something coming on the television I ought to watch, because he’d enjoyed it when he was a kid, and I remember thinking I wasn’t likely to get much out of something as ancient as that. But I watched all the same, and from the first moment I was spellbound.

I must have been very young, because Tom Baker was still the Doctor. He went to Paris, where an alien who had a machine that could speed up time and age people was trying to steal the Mona Lisa.  I was hooked. What kid wouldn’t be?

And that’s the thing about Doctor Who, which celebrates its 50th anniversary today.  “Imagine the pitch meeting for that!” people who like to think of themselves as grown-up say. “Well, it’s about this guy who travels through time in an old phone box. He’s hundreds of years old and he comes from another planet. He fights aliens and monsters but he never carries a gun, he relies on his intelligence. Oh, and the phone box is bigger on the inside than the outside.”

And then they tend to say things like “What drugs were they on?”

But they’re thinking about it the wrong way round. Imagine you’re a child hearing that pitch: who wouldn’t love it? To a child, there’s nothing far-fetched about a time-machine inside a phone box. Any more than there’s anything far-fetched about a wardrobe that’s a door to another world where it’s always winter and there’s a talking lion — C. S. Lewis, who also has an anniversary this week, knew that.

That’s why I never really got people who moaned about the special effects. What, you mean that’s not a realistic transdimensional time-machine? Well, show me what it would look like. They always seemed lazy to me, wanting the television to do the work of their imagination for them. It’s a story, it’s about the willing suspension of disbelief, and if Tom Baker told me the lumbering extra in the tacky costume was a terrifying monster, I believed him. I really did. Because that’s how children’s minds work.

If you believe there are monsters in the wardrobe, you’ll believe there are monsters in the police box, whatever they look like. Stephen Fry recently dismissed Doctor Who  as just a children’s programme, to the rage of its fans, but they all missed the point. It is a children’s programme, but there’s nothing inferior about that. Just as Harry Potter is a children’s book.

When you’re a child the universe is still full of wonder. You don’t think you’ve got it all explained, like Stephen Fry with his show-off’s knowledge and his atheist’s certainty. There could be a madman in a box fighting off Daleks and Cybermen.

But the really wonderful thing you discover about Doctor Who when you get older, is that some of it actually makes sense. Maybe not aliens stealing the Mona Lisa, but that phone box that’s bigger on the inside than the outside? Einstein’s Special Theory of Relativity explains that. And it turns out the Doctor was right all along, and time and space are the same thing, and you can travel around in it — even if, as far as we know,  it appears to be impossible to go backwards. Turns out those TV execs back in the sixties weren’t on drugs, they’d read their Einstein.

The universe is far weirder than we think it is. It’s even weirder than Einstein thought it was, God does play dice and things exist in two simultaenous contradictory states until you look at them. We don’t understand how it all works, and it can’t be explained away on an episode of QI.

When you’re a child, you’re okay with all that. Everything’s new anyway, you’re learning as you go along, it’s entirely possible that you’ll travel to Mars one day or some one will invent a time-machine; and if there are monsters in the wardrobe, it’s comforting to think there’s a Doctor somewhere who can fight them off with a jelly baby.

But for some reason people think that growing up means putting away all that wonder. You get bogged down with mortgages and pensions and school catchment areas, you start taking politics seriously and you think you know how the universe works and you have more important things to worry about, frankly.

Children know better. Politics is boring, and there might be anything out there. Absolutely anything. Even a time-travelling alien in a phone box.

Which is why I’ll be raising a glass to an old friend tonight. Happy Birthday Doctor!