Ireland's Jamie Costin finished 44th in the 50km walk this morning in conditions made brutal by relentless sun. Costin finished in four hours 15.16 minutes, more than half an hour behind winner Alex Schwazer of Italy, while team-mate Colin Griffin was disqualified.
Schwazer, a double world championship bronze medallist, broke clear around the 42km mark and covered the longest race in the athletics programme in three hours, 37 minutes, nine seconds, a new Olympic record.
Australia's Jared Tallent, who took bronze in the 20km event, went one better with silver on Friday, coming in two minutes, 18 seconds behind in a personal best.
World record holder Denis Nizhegorodov of Russia, 50km silver medallist in Athens, took bronze.
It was a hugely impressive performance by Schwazer, who took more than a minute off the 20-year-old Olympic record set by Vyacheslav Ivanenko in Seoul.
After Thursday's rain the sky was clear and conditions relatively cool when the field set off at 7.30 a.m., but it did not take long for the mercury to rise.
The heat meant that big gaps soon opened and the three medallists eventually broke clear from a pack of seven soon after the 30km mark and after 40k they had built a two-minute cushion.
Schwazer was the stronger, though, and burst 40 seconds clear with 5km to go. From then on it was merely a question of avoiding disqualification, which he accomplished safely to take Italy's first gold in the event since 1964.