Tim Key: I went to the pool for my bad back. But then I got in a race with a Japanese man...

(Ping Zhu)

I've just got back from the swimming baths and I feel thoroughly reinvigorated. Partly by the unnaturally generous exposure to chlorine, human flesh, and padlocks, and partly because things just became very competitive between myself and a Japanese gentleman.

I hate swimming, as a rule. I only do it because I have a bad back but, because my improvised 'stroke' is so erratic, it sends my spine into a spin and so – ironically, I suppose – my back deteriorates with each session. It has no real idea why I keep hauling it to the baths, and nor do I. It is dismal. I cut a depressing figure each time I waddle from the changing room and emerge at the water's edge. I stand there on the curb, hands on hips observing things, before lowering myself in and thrashing about until I spasm.

Today, there was at least a Japanese gentleman in the drink to spice up proceedings.

He was already in when my back and I arrived, and he was a joy to behold. Goggled and slim, he moved smoothly through the water like a lean, black-haired penguin, chewing up the metres effortlessly, pinging backwards and forwards like a metronome. I watched for 20 minutes, enriched by his performance. I felt reinvigorated by what I saw and almost called it a day there and then. But I knew I'd feel bad if I didn't at least dunk my thighs in, so I found the steps, added myself to the pool and began my laps.

We were like chalk and cheese. Him: fluent, serene, pushing himself from one end to the other easily. Me: an embarrassment; no two limbs on the same page, chaotic, like an owl finding himself in a fish tank and trying to adapt to it. It was like we were in different types of water. His seemed to lift him, keep him afloat, propel him almost. Mine felt thick and old. I could barely find a way through it.

With each length I managed, the Japanese man processed just under three.

Soon he was actually doing three lengths to my one. He seemed to be speeding up, and stretching his fingers to make sure of it. And looking across once he'd done it. And it was then that I realised: he was racing me.

You can't kid a kidder, and I knew what he was up to. He was racing me for kicks. Using me as a target, to improve his performance. The swine.

I enjoy doing that myself. In my life as a pedestrian I will often find myself racing some unsuspecting member of the public. I'll pick a finish line in my head – an HMV, some bollards, the top of an escalator – and I'll imperceptibly accelerate and nose them out at the final moment. A little Henman-style fist-pump, and I'm on my way.

But I didn't much like it coming from this Japanese chap. Clearly a talented sportsman, he was swimming through three times as many litres as me and enjoying a huge victory rush every 90 seconds. It seemed unfair. Without him knowing it, I also began to race. But I didn't have his tools, and he continued to cruise past me in the final metres. He seemed to smile as he slithered out and hit the sauna.

I watched him go in. And I waited. And then I followed.

I barely looked at the guy in the sauna. He didn't want to be the first to leave, and nor did I. The heat was unbearable. He was dying to defeat me, but I wouldn't budge. He had humiliated me in the pool, but this was my moment. He wanted it so bad. His Speedos were squeaking with the effort. My forehead was thick with sweat, but I wanted to even things up.

"Call it a draw?" I eventually said, my mouth dry.

"What?" He had no idea what I was talking about.

I left with as much dignity as I could manage. Japan 2-0 England. I waddled to the lockers.