Russia's Sergey Kirdyapkin today won the gold medal in the 50-kilometre walk in an Olympic record time.
The former world champion finished in three hours, 35 minutes and 59 seconds, almost a minute clear of Australia's Jared Tallent, who took silver for the second Games in succession, with China's Si Tianfeng claiming bronze.
Ireland's Robert Heffernan was fourth in a national record of 3hrs 37mins 54secs, just holding off Russia's Igor Erokhin on the line as both athletes were given the same time.
Si looked on course for victory when he wiped out a 20-second deficit and went clear of the field at the 35km mark, but when he faded Kirdyapkin took over at the front and was never in danger of being caught.
Italy's Alex Schwazer was unable to defend his title after being excluded from the Games following a doping violation.
Heffernan finished ninth in the 20km walk seven days ago and was also fourth in both walks at the European Championships in Barcelona in 2010.
The 34-year-old said: "I wanted to win an Olympic medal, it's been my dream. I did everything I could, it's hard to take to finish fourth. The last four years have been aimed at winning a medal at the Olympics so it's tough.
"The first 30km was just making sure I was refuelling, making sure I had the reserves to challenge on the last 20km. I had to be mature because you can get carried away by the unbelievable crowd.
"I stuck to the plan and it's just unfortunate I did not win a medal. There's nothing more I could have done."
Britain's Dominic King was 51st in 4:15.05, last of the competitors not to drop out or be disqualified.
Despite being the last man to cross the line, King received a huge cheer from the crowd and had even been exchanging hi-fives on the last two-kilometre lap.
"I didn't realise how fast I was walking so when I started to hi-five the first lot of people on the lap my arm soon became pretty tired after about 50m and I realised I had another 1,950m to go, so not everyone got a hi-five," the 29-year-old said.
"But I fully appreciate the support that came out today, not just supporting myself, but everyone in the field. It's a gruelling event and that can lift you."
King was examined by medical staff as a precaution after a race he admitted equates to more than four hours of agony, but was more concerned by an early warning he was handed during the early stages.
"Unfortunately I've had issues in the past with getting disqualified and I've been working on it for the last two years," he added.
"My priority was always to finish and the second priority was to get a personal best. I didn't do too bad today, it was my third fastest time ever and I had to get an eight-minute personal best just to qualify so medals were never going to be in the equation, but I feel like I got my own medal just by getting the biggest cheer of the day."
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