Part two of this anti-epic of mine - trying to get ready for the London Triathlon next month - begins in the rare intense sunshine of an English stately home in early summer. Readers of part one (Body&Soul, June 14) will recall that I was by no means optimistic about my first attempt at a triathlon, albeit at sprint distance, half of the Docklands Olympic distance. The running would be fine, but I'd be swimming in the open water for the first time and back on a bike for only the third time in two decades.

So I arrived for the Mazda Blenheim event last month full of fatalistic trepidation. There were thousands of people, triathletes and their families picnicking, changing, changing back (triathlons are held in timed “waves” over a couple of days), flaunting their medals, carrying their gear and their bikes between their cars and the large area, in the great courtyard, which was the all-important “transition” area.

Where once the Duke of Marlborough and Lady Sarah received their guests, or flogged their ghillies, or whatever they did, several hundred bikes were stacked in ten rows. Into and out of this place came swimmers returning from the chilly Blenheim lake, ready for the bike stage; bikers who had completed the three hilly laps and were about to run; runners who had just completed the whole thing and were happy to die, or to picnic. And people like me who hadn't begun yet.

We looked like leggy penguins

The atmosphere was collegiate. Though we were absurdly badly matched as athletes (there were fatter men than me, but not many, and a few older ones too), there was always camaraderie between the participants. Down by the lake the men of my midday “wave” stood around in the heat and bonded. Then in our uniform of black wetsuits and white swim-hats we lined the pontoon, looking like a leggy species of freshwater penguins.

It was so cold in there. So cold. It was a relief when at last the signal was given to begin the tick-shaped course, but after five minutes the distance seemed so great. As I toiled at my breaststroke, gradually falling to the back, I appeared to make no progress. It had been easy but boring in the pool; here it felt dangerously hard - 750m is not much. I got to the end buoy and struggled up the bank, up the short hill and crossed the first timing line. Only two men were behind me. I wanted to kiss them.

Peel off wetsuit revealing shorts and shirt. On with bike helmet. Swig of Lucozade. On with cycle shoes. Wheel bike to start point. Get on bike. Wobble. Fail to get right foot into pedal clip. Wobble more. Get started. Hill. OK. More hill. Have to get off. Utter humiliation. There's only one other hill walker and I think he has broken his leg. Still one advantage of going in overlapping “waves” is that you can never be absolutely sure that you're last; 20km (12.4 miles) of walking uphill, gripping the brakes as I career downhill and chunking along satisfactorily on the flat, and it's over. Just the run left.

But I have nothing left. I took no energy gels, thinking it would be unnecessary at this distance. As I begin the run I find my legs reluctant to move. To my amazement, when I get to the hilly part I can't carry on and over a distance that is half my normal Saturday run, I find myself walking. Still, I cross the finish line among hundreds of happy men seeking out spouses and children, and get a drink and a cake and another cake and a third cake and a banana. It is a wonderful occasion, but the time will be hopeless.

It really was. They texted it to me: 23 minutes for the swim, which is actually OK, except can I really do twice the distance? 1 hour and 10 minutes for the bike ride, which is about the speed of a commute into London and totally pathetic. I did the run in mumbleburble (I am not writing it down here).

Up for the London to Brighton bike ride

One week later found me at 7.30am, once more in sun, on Clapham Common, South London, among thousands of cyclists, about to take part in the British Heart Foundation's annual London to Brighton bike ride. When I last did this event in 1983 there were a couple of thousand of us, I think. On this day, 27,000 had registered to take part. There was every conceivable bike, from yellow-jersey contender to maiden aunt's, and every conceivable rider, from implausibly sinewy to polyester moose.

The idea was to find out if I could improve my cycling and make it less painful; 55 miles should show it one way or the other, and the weather was kind. Well, there were glorious if panicky swoops, companionable stops in fields to drink coffee and eat hot dogs, grinding uphills in which I would crunch my gears and have to get off, and fabulous straights in which my running legs would help me to overtake all those who had passed me going up or down the hills.

On Ditchling Beacon, the infamous K2 that stands between a cyclist and the sea, I walked, as did three quarters of my wheely brethren. Towards the top a lone man in his forties passed us, still on his bike, one hand on the handlebars, the other holding his mobile phone, into which he gave an unfatigued commentary on his progress. The day had been so good I didn't even hope that he'd hit an oil slick on the way down.

I got to Brighton, fell sideways through a crash barrier to celebrate my arrival, and realised that I had blisters on my palms and what I imagined to be bruises on my ischial tuberosities (look it up). But my bike confidence was much greater. The only trouble now, was this: the fortnight's exertions had exhausted me. I rested for a week. Then took it easy for another week. Then woke up and realised that the London triathlon was just 35 days away. Ohmigod.