Driving along the M4 for one of the highlights of the domestic triathlon racing calendar, the Nokia Windsor Triathlon, the competing triathlete isn't hard to spot.

It's not the sticker in the back of the car or even the type of vehicle they drive.

It's the gleaming frame dangling from the bike rack or the shiny new wheels pressed against the rear windscreen that give the game away.

In recent years triathlon has become increasingly visible as a sport and attractive to its participants.

It wasn't always so. 

Almost 20 years ago, when the fitness boom in the UK was in its infancy, the very first Windsor Triathlon took place amid some cynicism.

"Trying to get people involved was like missionary work," says John Lunt, the founder of  Human Race, an events company now putting on more than 30 events a year including half and full marathons, open water swimming races, duathlons and triathlons, including Windsor.

In the early 1990's the idea of swimming 1500 metres in the Thames, then cycling 40km around Windsor before finishing off with a 10 kilometres run didn't attract much enthusiasm or interest.

Just 200 trail blazers lined up for the first Windsor race in 1991.

This June Windsor celebrated its 20th running with 2,500 athletes of all ages, shapes and sizes willingly plunging into the Thames knowing they were the lucky ones.

It's a race which has long been one of the most prestigious events on the summer calendar, and all 2,500 slots for the 2010 event sold out within three weeks of online registration opening. 

Another 1,200 were on the waiting list.

"If you haven't done Windsor you haven't competed in all the big events in Britain," says Ian Parker, who's completed nine in total and now helps as one of a small army of volunteer staff.

Back in the early days, when triathlon was still relatively new, it was just the super fit who competed.



Today, while not a mass participation sport, triathlon, and Windsor in particular, caters for a range of athletes with varying experience and ability.

There are triathletes participating for charity, others who want to dip a toe in the water with the shorter, 'Sprint' distance (750m/29km/5.5km), age group competitors who start by age and gender and, finally, an elite field of 70 of the country's top triathletes who start at the end.

Today the sport's no longer the domain of a fit few. 

Instead a pre-race Expo features music, clothing and equipment stands, refreshments and a long line of massage tables for the eager triathletes.

And there's certainly no shortage of eye catching and, at times, eye wateringly expensive kit.

"It's totally changed," says Parker. "You used to be able to get your old bike out of the shed and compete.  Now you have state-of-the-art bikes and wetsuits."

Adrian Smith, director of Total Fitness Bath, one of the exhibitors at Windsor, agrees. "'I raced the first race," he says. "The kit I used was basic. Now everything is very specific."

And expensive.

"You get people who spend £4,000 or £5,000 on a bike," he says. Or there are those who want carbon front and back wheels and are happy to pay £2,000, or more, to have them.

"You can go crazy," Smith says. "But it's still the person pedalling the bike at the end of the day."

And as those gleaming machines and shiny wheels get put away for another day, the 2,500 or so athletes who own them probably feel a little sorer than they did at the start of the day.

And, no doubt, exhilarated at the achievement.

Happy Birthday Windsor Triathlon. 

Here's to the next 20 years.

Cathy Wood was editor of the Daily Mail Ski Magazine before moving to become ski correspondent on the Daily Mail. She later became travel editor before going freelance. She represented Great Britain at elite level triathlon and writes on travel, skiing and sport.