When he was in the Scouts, my friend Minto went through a phase of speaking flippantly about his father. His dad was a leader and, at six feet four, was seen, wrongly, as stern and imposing.

Looking back, I think Minto’s ploy was a perhaps unconscious attempt to soften his friends’ image of a man he was deeply fond of. One phrase sticks in my mind. “Aye, the old boy’s kicked the half-century!” His father was 50. It seemed impossibly old.

Aye, well, I’ve kicked the half-century myself and I have learned many truths over the past few years.

When I was a wean, I thought my parents watched Dr Who and Batman along with me, because they liked them. As a teenager, I reckoned they’d been watching them out of a sense of duty to keep me company. I now realise that they watched these shows because they actually did enjoy them.

While I am now unlikely to find Norman Wisdom’s slapstick so funny that I’d risk serious ligament damage (Mr Grimsdale!) laughing at him, my teenage self would be surprised at how much I remain entertained by the films and TV programmes that grabbed me as a child.

Similarly, when my mum and dad listened to Glenn Miller, I used to assume that this was music you grew into as you aged. It never occurred to me that they were simply maintaining a love of the music of their youth, until I found myself doing the same.

Had I stayed in teaching, there is a chance I could be about to retire. The post I held was surplus to the new world of faculties. I’m sure somebody would have found a package for me. To remain solvent, I would have felt obliged to seek supply work and that in itself would have been enough to make me turn down the chance to go.

When I was seconded, I was called back to school one day a week to cover the classes of a colleague who herself had a temporary post. It was the worst classroom experience I’d had for years. Despite being in a school I loved, teaching my own subject, I found it difficult to settle. The pupils didn’t know me and I failed to win all of them over on one day a week.

It was a humbling experience, one that reminded me of one of the reasons that teaching kept me young. Every so often, even during the many good times, something happened to make me feel I was still just out of short trousers myself, that I couldn’t be in my 40s because someone of that age could not have learned so little.

That’s downbeat. The main reason that teaching kept me young, and the same applies to my new “lab rat who gets to run CPD courses” role, is that I have not lost the enthusiasm for science that the wee boy who wanted to build a rocket out of oil drums possessed.

I feel immensely lucky I have been able to kick around for half a century puzzling, dabbling, scribbling and blethering about the subject. We’re going out for a birthday meal this evening. I’ll be recording Dr Who.

Gregor Steele’s presents included a toy meerkat, a McLaren team baseball cap and a cuddly photon.