Each day of the Games we will bring ten facts you may or may not know about the great sporting spectacle that is the Olympics. Today we have see the star man going for a unique feat
It's a big day for the men on the athletics track, with five golds to be decided. In the 200m all eyes will be on Usain Bolt, as he bids to become the first man to win the Olympic sprint double twice - and, indeed, the first man to retain the 200m title. The last pre-Bolt sprint double was by Carl Lewis in 1984, but in Atlanta in 1996 Michael Johnson won both the 200m and the 400m, a unique achievement by a male athlete.
In the 800m - won by Steve Ovett in 1980 - the hot favourite is David Rudisha. Kenya won gold last time, too, with Wilfred Bungei. In 1996 the Norwegian Vebjorn Rodal won gold - setting an Olympic record that still stands - and became the only athlete ever to win an Olympic final after qualifying for it as one of the fastest losers in the semi-finals.
Few Brits of a certain age can watch the decathlon without getting all nostalgic about Daley Thompson, and the nonchalant way he mooched through the event, almost inevitably coming out on top. Thompson, who took gold in 1980 and 1984, remains only the second man to win the decathlon twice - after the American Bob Mathias, who took gold in London in 1948 when only 17 (still the youngest Olympic athletic champion of all) and retained the title in Helsinki in 1952. Mathias later became a US Congressman.
The final men's gold today is in the triple jump, another event in which we've become accustomed to British success ... but not this time. Back in the days before Jonathan Edwards and Phillips Idowu, the Russian Viktor Saneyev won gold in 1968, 1972 and 1976, and missed out on a fourth gold in Moscow by just 11mm, taking silver behind another Russian, Jaak Uudmae. At the first modern Olympic Games, in Athens in 1896, the triple jump was the first event on the programme: so the winner, the American James Connolly, was the first Olympic champion since 369AD.
The only women's athletics medal to be decided today is in the women's javelin. Tessa Sanderson competed in six Olympics (a record for a British woman), and won gold in 1984, but GB's Goldie Sayers missed out on qualification this time, hampered by injury. The javelin was added to the women's Olympic programme in Los Angeles in 1932, when it was won by the multi-talented allround athlete Mildred "Babe" Didriksen - she also won the 80m hurdles and was second in the high jump, and later became a leading golfer. And in 1952 Dana Zatopkova won, not long after her husband, Emil Zatopek, won the men's 5000m the same day.
The indoor swimming has finished - so today it's outside to the Serpentine and the women's 10km marathon swim. Keri-Ann Payne was just pipped for gold in Beijing, and she's one of the favourites again this time. She's won the last two world championships, and was the first athlete from any sport to qualify for Team GB in London. Having swimming events outdoors is a throwback to the first modern Olympics, in Athens in 1896, when the swimmers competed in chilly and often choppy seas in the Bay of Piraeus.
After Britain's first dressage gold medal, in the team event earlier in the week, there's a chance of another first in Greenwich: GB have never before won an individual dressage medal of any sort either. The last three individual golds have all been won by Anky von Grunsven from Holland (who is taking part in her seventh Olympics in London), and the four before that all went to German riders. Lis Hartel, a Danish woman, won silver in 1952 and 1956, despite being unable to move her legs after a bout of polio.
As the football tournaments reach their climax it's the female final today. Women's soccer was added to the Games programme in Atlanta in 1996, when the USA won a popular home gold, and they won again in 2004 and 2008, with Norway intervening in Sydney in 2000. And the States will be going for a hat-trick this evening at Wembley, when they take on Japan. America's captain Christie Rampone has won more than 250 caps for the national team, and was a member of the last two Olympic gold-medal teams.
In Dorset it's the medal race in the men's 470s, with Luke Patience and Stuart Bithell almost assured of at least a silver medal - but they will have to finish a couple of places in front of the Australian boat, which has won the last two races, to turn it into gold. Britain has never won the 470 (an Olympic event since 1976), and, rather worryingly for Patience and Bithell, have taken silver at three of the last four Games.
And finally the first-ever Olympic medals in women's boxing will be decided today, in the finals of all three weight categories. There's a chance that the first such gold medal could go to Britain, as the flyweight final features Nicola Adams, a double silver medallist at the world championships.