Evening Standard man takes on challenge of three races in three countries in a day

When British Olympic hopeful Vanessa Raw swam past me for the second time in a lake in Paris, I knew I was out of my depth.

It's not often one gets to race against some of the world's top athletes and the chance to do so in the first ever international triathlon was irresistible.

The idea was simple: three events in three capital cities in 24 hours.

The most exhausting day of my life began in the dark with a 1.5km swim at 7.30am in the French capital. The competitors — world-class athletes and 60 amateurs from Britain, France and Belgium — were then taken to Brussels for a 40km bike race before ending with a 10km run in London's Regent's Park.

Having been entered only two weeks earlier, my training could be described as minimal at best.

As I spluttered through the freezing lake in Paris, it quickly became apparent my laissez-faire approach wouldn't wash in the waters of the Bassin de la Villette and before I knew it I was last, helplessly thrashing as more than 100 white swim caps disappeared into the distance.

An hour later we were whisked off to Belgium by hosts Eurostar, the London 2012 Olympics international rail provider, where a challenging six-lap race through Brussels' streets awaited.

With closed roads and dry conditions, I jumped on my racer in the shadows of Heysel Stadium, hoping to make up for a lacklustre performance in the swim. This time I was lapped three times by former world triathlon champion Alistair Brownlee, as he demolished the course a full half-hour ahead of me.

Pedalling away, I began to lose hope when former Great Britain Olympic 400m runner Iwan Thomas passed me on the bike for the second time, bellowing words of encouragement.

Eventually I rolled over the line desperate to lie down, throw up or just cry, but instead I had a train to catch with London calling. The skies over Regent's Park opened as we began the gruelling final leg of the competition.

As a practised half-marathon runner, 10km should have been a walk in the park — but the swimming and cycling had left me feeling close to death.

This time it was U23 world triathlon champion Jonathan Brownlee's turn to put me in my place as he raced to victory in an impression of Road Runner to my Wile E. Coyote. Rain poured down as I finished, to cheers from amateurs and Olympians alike.

A seasoned triathlete had bet me this would not be my last triathlon and as I crossed the line I knew I'd be back for more. Team GB, I'm on standby.