No-one knows categorically how this happened and that's the really scary thing about it - it could happen to anybody

Mark Richardson on his positive test

Richardson (l) celebrates relay gold at the 1998 European Championships

"I'm passionate about my sport and I'd never do anything to put it in jeopardy," he said.

"Morally I'm innocent. In hindsight I wish to God I hadn't taken any supplements.

"No-one knows categorically how this happened and that's the really scary thing about it. It could happen to anybody."

Once he became embroiled in the on-going nandrolone saga, Richardson's whole athletic career was put on the line.

The Windsor-based runner is one of British athletics' most loyal ambassadors and though he has a host of trophies, he has yet to acheive his ambition of winning individual gold at a major international event.

1992: As a 20-year-old hopeful

Britain has always had a fine pedigree in the 400m.

When Richardson burst onto the scene in 1990, winning bronze at the World Junior Championships as an 18-year-old, he was seen as the next great hope in a prestigious line of runners that have included Derek Redmond, Roger Black and John Regis.

Such was his promise he was chosen to represent Britain in the 1991 World Championships.

He ran in the heats of the 4x400m relay, helping the team reach the final where the legendary quartet of Redmond, Black, Regis and Kris Akabusi famously defeated the Americans to win the gold medal.

Richardson, the reserve, stood on the sidelines and had a glimpse of the glory he hoped to achieve for himself.

1994: Returning to fitness at an indoor event

But a combination of bad luck, injury and big-day nerves mean that nine years on, he is still looking to win individual gold at a major international event.

He has come close on many occasions.

In 1992 he won Olympic bronze with the men's 4x400m relay team.

But in 1993 injury struck and plagued him on and off for two years.

Having believed he could win the 1994 European Championships in Helsinki, he was forced to watch "a guy I knew I could beat" take gold.

While studying a sports science degree at Loughborough University, Richardson battled back to fitness and re-launched his career in style.

1995: Set up a sprinting school in Windsor

In his first full season back he won the European Cup and the AAA Championships and had commentators speculating that he heralded "a new era of one-lap running" for Britain as the likes of Black began to fade from the scene.

By 1996 he was considered to be Britain's top 400m runner and an Olympic medal prospect.

But once again he misfortune struck as he fell ill with food poisoning at the Olympic trials and managed only fifth place.

He still went to Atlanta and again performed superbly for the relay team, running the fastest leg as Britain took silver.

Richardson was not only a fine ambassador on the track, he also did great work off it - after graduating from Loughborough he helped set up an athletics academy designed to help find the next generation of British stars.

Although based at the prestigious Eton College, Richardson's lottery-funded School of Sprinting aims to take in youngsters from all local authority schools in the surrounding area.

Iwan Thomas: Still holds the British record

Richardson, himself educated at Claire's Court in nearby Maidenhead, says he was motivated by his desire to "put something back" into the sport.

1998 was going to be Richardson's year.

He began it be becoming only the second man in nine years to beat 400m superstar Michael Johnson and won the European Cup at a canter.

But there was a new young threat looming.

Welshman Iwan Thomas, who also beat Johnson in the same race, clocked a new British record with 43.36.

The battle between the pair in the build-up to the European Championships was intense.

Richardson twice ran within 0.1 secs of Thomas' time, beating him five times in six races before the final showdown in Budapest.

1998: Richardson's anchor leg was decisive

This was Richardson's best chance of the major gold he so craved.

He began as clear favourite, aiming to become the first Briton to break the European 400m record for 60 years, but he ran a disastrous race.

Thomas took gold while Richardson trailed in third with a poor time.

It was one of British athletics' most successful weeks, the team winning a total of nine golds, four silvers and three bronzes.

1999: Disappointing sixth at Seville

But Richardson, with a consolation gold in the relay, admitted he was "devastated" by the defeat.

He pulled out of the World Cup in a bid to regroup in time for the forthcoming Commonwealth Championships but the tactic backfired as Thomas' competitive edge saw him take gold again, Richardson finishing in second.

Richardson was once again Europe's leading runner at the distance last year but managed only sixth at the World Championships in Seville.

Thomas' British record still eludes him.