To say that David Millar's career was one of highs and lows would be to simplify it in the extreme, but it is a journey which has now, finally, come to an end.

Millar finished 21st in the Bec Cycling Club climb in Surrey on Sunday and hung up his helmet for the final time as one of the most successful cyclists that Britain has produced.

The 37-year-old contested 24 Grand Tours throughout a 17-year professional career and won 10 stages, as well as having become the first British rider to have worn the leader's jersey in all three.

The Scot also has two world championship silver medals, as well as Commonwealth gold and bronze medals from the 2010 Games in Delhi. It is not, though, the silverware for which he is best known.

Millar's potential on a bike was spotted early: signed by the professional team Cofidis in 1997 at the age of 20, he won his first Tour de France stage just three years later but it was in 2004 that Millar really hit the headlines. In June of that year, he was busted for doping, an event which would go on to define his cycling career and indeed, his entire life.

The Scot had succumbed to temptation and began taking EPO, something which was almost the norm in that era of the sport. He subsequently served a two-year ban from the sport. Unlike so many other dopers, though, Millar did not allow the ban to end his career. He returned and it was during this second part of his career that Millar's reputation would be resurrected, enhanced even.

Some will never forgive Millar; once a doper, always a doper, they say. Many others see the Scot as a pivotal figure in nudging cycling towards the clean sport that is so lusted after. He showed significant remorse for his actions and, since he served his ban, has worked tirelessly in educating younger riders of the risks they may face.

He is also one of the few riders who fully engage with the drugs issue in the public sphere, openly and eruditely commenting on whichever doping issues are the topic of the day. On his return, Millar also - alongside Jonathan Vaughters - developed his own team, now Garmin-Sharp, which has been at the forefront of cleaning up the sport from the inside.

Millar experienced both the good and the bad of cycling.

He is one of this country's most successful athletes and his retirement from competitive racing is unlikely to mean that we see or hear no more from him.