I can’t remember her exact phrasing but it was along the lines of: “Gonnae watch that wean’s heid, ya pure, oh no, that’s pure ...” I said sorry immediately, and then kicked myself for doing so. Fathead’s cranium had cleared the steel doorframe by a good inch and a half; even if he’d imagined a football coming whizzing towards him and raised himself to fire off the perfect header, he would have cleared it, just about.

But headroom wasn’t foremost in my mind, so I did feel somewhat guilty. Had Minor Fathead been walked teeth-first into stainless steel on his dad’s shoulders he could easily have thrown his arms aloft in a show of dramatic disgust, at which point he could have backflipped into thin air and thick rubber flooring.

My focus had been trained exclusively on checking there was a lift to step into, with a proper floor. Call me old-fashioned but I wasn’t prepared to plunge self and Minor Fathead down a gaping lift shaft and have my last tormented thoughts soundtracked by someone peering through a gap four floors above, saying: “He should have watched where he was going – he was pure just looking upwards.” The stakes, in other words, were mighty high. It would have meant ambulances, my face splashed across the Evening Times. Sunday Herald writer. Shafted.

Holding babies on shoulders carries such risks, but it’s something few fathers can resist. Watch a chimp running from one side of a cage to another – bandy legs, hands behind head, goolies swinging freely in the wind: that’s the look dads are going for.

Sure as day, baby will be hoisted on to papa’s man-shoulders at the earliest opportunity. You don’t know why you’re doing it. It’s just nature. Oh, it feels great.

But why? Maybe because you’re walking through the town centre like a chimp, your oxters showing, your goolies swaying freely in the wind. Oh, it feels great. You are friendliness and pheromones personified. You have supplemented your own head with a much smaller and fatter head, which people are inevitably drawn to. “Look,” they say, “a baby on his dad’s shoulders – what a thoroughly unusual sight.”

For babies, there’s a reverse dissociation: they’ve somehow supplanted their body with yours, which is bigger and more chimp-like and can be steered through the busy streets like an old nag. Better still, they can yank your hair out at the follicles, clump by sodden clump.

By the time you get to the fourth floor lift of a department store you look like Friar Tuck, but with blood running down your cheeks. You don’t mind, no, really, it’s fine. Just check there’s a floor to step on to. That’s a boy, there. Oops, now. Watch the wean’s heid.