Six-time Olympic champion Sir Chris Hoy is to retire from competitive cycling.
The 37-year-old Scot was contemplating continuing until the 2014 Commonwealth Games in Glasgow, but confirmed he was quitting the sport at a lunchtime press conference in his home town of Edinburgh on Monday.
He said: "It was not a decision I took easily or lightly but I know it's the right time. Today I'm officially announcing my retirement and it's a decision that I didn't take lightly and I thought about it very hard.
"The reason for that is that I thought I've got every last ounce of energy out of myself. "I got to London and I don't think people realise how much that took out of me."
Hoy is Britain's most decorated Olympian after his haul of two gold medals at London 2012 saw him surpass rower Sir Steve Redgrave's record of five.
As well as six Olympic titles, Hoy's 13-year career featured 11 world titles and two Commonwealth crowns.
His final race was the Olympic keirin final on August 7 last year on the final day of the London 2012 track programme.
He won the event and overtook Sir Steve Redgrave as the Briton with the most Olympic gold medals.
Hoy said: "I think in sport, at the highest level you're dealing in such small margins and you can tell when you're good but not good enough.
"The recovery, the whole injury aspect was becoming more of an issue. There was never a moment where I said 'never again'.
"I'm happy, I'm satisfied. There is no lingering doubt. I've done everything I can."
Explaining his decision not to continue to next year's Commonwealth Games in Glasgow, Sir Chris Hoy said: "To try and go on for another year would have been too much and one year too far for me.
"I didn't want to turn up to wave to the crowd and wear the tracksuit. I wanted to be there to win a medal for Scotland. Because I don't feel I can do that, I would rather step aside and let somebody else take my place.
"It was very emotional coming in (to the press conference) and I was trying not to watch the video montage with the sad music. I don't want it to be a sad moment. I want to celebrate it and be happy because I know it is the right decision.
"It's a hard time, one moment at the end of your career when you have to say enough's enough. There's always a temptation to go on, perhaps too long, and it's not that I'm frightened of losing. I feel as if I can't ask for any more.
"I've done the very best that I can. I've had an amazing career and have so many people to be thankful for that but this is the end of it."
Glasgow 2014 chief executive David Grevemberg said he respects Sir Chris's decision and paid tribute to his achievements.
"Sir Chris is not only Britain's greatest Olympian, he is an inspiration and a first-class ambassador for Scotland and the Glasgow 2014 Commonwealth Games.
"We look forward to continuing our excellent relationship with him as, together, we share the excitement and potential Glasgow and Scotland's Commonwealth Games hold for the next generation of athletes aspiring for gold."
British Cycling president Brian Cookson hailed the "unparalleled impact" Sir Chris has had on his sport and said he will continue to be a role model.
"It goes without saying that not only is Chris an absolutely phenomenal athlete but he is also an exceptional individual. The fact that he's acquired six gold medals and is Britain's most successful-ever Olympian is testament to this," Mr Cookson said.
"But Chris has done so much more for cycling. He was one of the first track riders to propel cycling into the mainstream back in 2008, bringing track cycling to new audiences and inspiring thousands of people to get on their bikes.
"Chris has always been a fantastic role model. His professionalism, passion for the sport and his determination to succeed at the highest level is central to the Great Britain cycling team ethos and is something that he has helped to foster amongst his colleagues as they look ahead to Rio."
Hoy won a medal at his first Olympics in Sydney in 2000 and his first gold four years later in Athens. But it was in Beijing that he established himself as one of Britain's greatest sportsmen.
He won the individual sprint, Keirin and team sprint titles in 2008, becoming the first Briton in 100 years to win three gold medals at a single Olympics.
In the aftermath he was named BBC Sports Personality of the Year and knighted in the Queen's New Year Honours.