Race-day weather couldn't have been better - fresh and sunny - but things below water weren't so good. The Thames was unusually fast-flowing and much of the 1,500m swim is upstream. I started in wave 17 (men aged 25-29) at 7.20am and it was a job just to tread water as we waited for the off. And then there was the piranha-like thrashing as 70 men in wetsuits clashed elbows and hips in an effort to get ahead.

The river was so murky thanks to the high flow that it was impossible to see an inch in front of your face. The first sign of an impending crash was the crunch of a heel in the ribs. We spread out after a few hundred metres and I began to find my rhythm, broken only by entanglement with a stick and a near miss with a moored barge. Once round the turn buoy it was a sprint downstream to the out. I got out (left) after 27 minutes. All was going to plan.

Once shod and helmeted it was a relief to be on the bike (below). I went out hard and soared past riders, averaging 21mph over the 26-mile course. It didn't take long before riders began overtaking me. First there came a distant whirr and then they would pass, sporting tear-drop helmets tested in wind tunnels, aerobars that place the arms forwards like Superman's, and rear disc wheels. Hearing these guys slicing through the air on their £4,000 machines was like being overtaken by a two-wheeled Starship Enterprise.

My thighs were smoking back at transition - a pen the size of a football pitch in which 2,500 bikes were racked on scaffold stands. Trainers on, the first lap of the 10km (6.2mi) course around Windsor was a struggle - my muscles turned to jelly until they adjusted to pounding rather than pedalling. The course took in a mean hill up past the Castle (where President Bush's visit passed unnoticed by competitors and the excellent crowd) but the rest, thankfully, was flat.

By the last of three laps I felt like throwing up. But, had I stopped to breathe (or puke) I don't think I could have started again - momentum and grit were the only things keeping me going. I managed a sprint across the finish line (below) and was delighted to see on my watch, through the sweat, a time of 2h32m, which can't be a bad time for a first-timer. The pen behind the line was a picture of pain as grown men whimpered with effort.

The elite waves went after the all-comers. Richard Stannard took the men's title with a time of 1h53m: Andrea Whitcomb was the first woman home in 2h06m. Another man who did well in my age group was F1 driver Jenson Button, who managed 2h23. Earlier he'd been spotted inflating his own tyres with a budget Decathlon track pump - no pit crew for him at this race.

A big thanks to Human Race for impeccable organisation. Getting 2,500 people round three courses in a busy town packed with tourists and spectators is an extraordinary feat and one they pulled off brilliantly. Entry for next year's triathlon will no doubt be open soon.

I still hate running but it's possible I've caught the triathlon bug (in more ways than one - my stomach hasn't been the same since - all that swan poo in the Thames I reckon).

I'm considering a late entry to the The Independent-sponsored Mazda London Triathlon on 10 August. It's quicker, they say (no raging torrent for the swim apart from anything). It would be nice to break that 2h30m mark...