I REFER not to cleanliness.

Cleanliness is next to godliness. But there can be no such thing as cleanliness. Hence that's a subject we can't discuss here.

Let me tell you what I'm talking about. Some of you may know Sheldon Cooper from American nerdy comedy The Big Bang Theory. He's obsessive, punctilious and addicted to routine. And he has his spot.

Loading article content

This is his seat in the room, and God – damn, how did he get back in here? – forbid that anyone else should sit there. It is, he says, "my spot".

Now, this always gets a laugh and is indeed comedic, but I've been surprised to find that this business of having a spot really does hold sway among you Earthlings.

It's something I discovered at exercise classes. I'd turn up for the first time at a long-established one and put my kit bag down at some spot around the room, where we all got changed. And then I'd find someone looking a bit miffed.

They weren't catastrophically annoyed, as Sheldon would be. But they were distinctly dischuffed. It took me ages to work out why. And then I realised: I'd taken their spot. Even though it was just a random space round one of the four walls, it was their space, from which they drew comfort.

Recently, starting a new yoga class, I worried that the same thing would happen. I switched the spot for my mat a few times during the first weeks, then fretted that I might have put somebody out. Then I thought: to hell with it. Because that's the kind of fellow I am.

You may have experienced something similar visiting friends, after inadvertently sitting in father's seat or some such. This territorial atavism always makes me laugh. Until someone takes my spot.