I am struggling to imagine Colin getting into the Lotus position. But he is serious. He is deadly serious. He intends to become a Yogi.

'Is there ... a name for Gay Men's Yoga?'

'I don't know. Probably Goga. I'll find out when I start. We have to begin to look after ourselves, Dan. We're in our thirties now. We are very old men indeed.'

He looks at me, solemnly, and with what seems to be real pity in his eyes. Is it because he sees in me the man he used to be? The man before self-reflection and Gay Men's Yoga? Is it because I am unenlightened? Is it because ... he has changed?

'Shall we have another quick pint?' he says. 'And then I'd better go, because it's curry night.'

No. It is not because he has changed.

But as I trudge home from the pub, I think about Colin's decision. And then I think about why I'm trudging. When did I start trudging? What has happened to my youthful bounce? Where is the spring in my step? Why do I not feel supple, or lithe? Colin's going to feel supple and lithe - shouldn't I?

But no, I tell myself. I am just feeling a little worn down. I've been on a book tour recently, eating bad food, stopping at motorway services halfway home from Norwich or Milton Keynes or Birmingham at nearly midnight, buying sausage rolls or cans of cut-price Lilt. This is just a phase, I tell myself. I'll be back to normal soon.

And then I realise that being back to normal still involves sausage rolls and cans of cut-price Lilt.

When I get home, I sit down at my computer.

I type 'supple' and 'lithe' into Google. Something deeply unsuitable comes up. I blink a couple of times but the images stay in there. I think I have seen what Goga can lead to.

I wander into the kitchen and make myself a cup of tea. I'm OK, I think to myself. I may not be supple. But I'm supple-ish. I'm lithe-esque. That's OK, isn't it?

I notice a crumb on the kitchen floor, and without thinking, I bend down to pick it up. It is easy. Ha. Take that, Colin.

But on the way up, something terrifying happens. As I straighten, I hear myself making a noise. A strange and yet strangely familiar noise. A sound I have heard my dad make. A kind of soft, involuntary 'aah' sound. A sound that signifies the end of a short burst of unusual exertion. The sound he would make after picking up a pencil, or stacking a garden chair.

A middle-aged sound.

I run to my computer, and I find a website.

Yoga for Beginners.