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 some swimmers and shooters are in focus
One of the highlights in the pool today is the women's 100m backstroke final, an event won in 1956 by Judy Grinham, a 17-year-old from Neasden in north London. At Sydney in 2000 the race was won by Diana Mocanu, a first swimming gold for Romania: in celebration, she was given a car. The bad news was neither she nor anyone in her family knew how to drive.
The winner of the men's 100m backstroke in both 1968 and 1972 was the East German Roland Matthes (he won the 200m both times, too). A few years later Matthes married Kornelia Ender, who won four gold medals herself - but their children couldn't make the most of their gene pool in the pool.
Australia's Leisel "The Diesel" Jones completed an unusual set of medals by winning the 100m breaststroke at Beijing - she'd been third in Athens in 2004 and second in Sydney (when only 15) in 2000. Susie O'Neill, Australia's "Madame Butterfly", achieved a similar triple in the 200m fly. But Jones is back again in London, the first Australian swimmer to compete in four Olympics.
The men's 200m freestyle has been won by several of swimming's biggest names over the years: Mark Spitz in 1972, Michael "The Albatross" Gross in 1984, Pieter van den Hoogenband in 2000, Ian Thorpe in 2004, and Michael Phelps in 2008. Back in 1900, though, the race took place in the River Seine, and all the participants recorded faster times than expected as the tide was in their favour. Fred Lane, a diminutive Australian, completed a double - he also won the 200m obstacle race, in which he had to negotiate a rope and two rows of moored boats.
On the rifle range, today sees the men's skeet event: it's the most cowboyish of the Olympic shooting disciplines, with competitors keeping the gun at their hip until the target is launched. At Barcelona, the event was won by a woman - Zhang Shan from China - who became the first female to win a mixed shooting event at the Olympics. But it had already been decided to segregate the sexes after this, and she couldn't defend her title - although she did finish eighth when a women's skeet event was added in 2000.
The men's Laser yachts have their first outing today: in 2008 the event was won by Yorkshireman Paul Goodison, but in 1996 and 2000 it was the stage for two memorable duels between the Brazilian Robert Scheidt and Britain's own Ben Ainslie. In Sydney Ainslie sailed rings around Scheidt - literally - in a successful attempt to keep him low enough in the standings in the last race to hang on for British gold. But in Atlanta four years earlier Scheidt scraped home, forcing the 19-year-old Ainslie into a mistake in the vital final race. In the BBC commentary box, Desmond Lynam was worried about the pronunciation of Scheidt's name (yes, that is how you say it!) and memorably intoned: "So that's silver to Ainslie, and gold to ... the gentleman from Brazil."
In the boxing, today sees the entry of the flyweights. Britain supplied the champion in Melbourne in 1956 - little Terry Spinks from West Ham, who discovered a couple of hours before the final that he was almost a kilo over the weight limit. A furious session of skipping ensued, with his coach shutting all the doors and lighting the fire in the middle of an Australian summer: Spinks sweated off the extra poundage, and had enough energy left to see off his opponent in the final.
Also starting at the ExCeL are the light-heavyweights. This was the category in which Muhammad Ali - then known as Cassius Clay - won gold in Rome in 1960. Forty years before that, another American won it in Antwerp in 1920: Eddie Eagan later won a bobsleigh gold too, and remains the only person to win gold medals at both the Summer and Winter Olympics.
The men's double sculls gets under way today at the rowing centre at Eton Dorney. This wasn't the event dominated by Redgrave and Pinsent: in fact Britain hasn't won gold since the Olympics were last in London, when the scratch pairing of Dickie Burnell and Bertie Bushnell came out on top. Burnell's father also won Olympic gold in London (in the eights in 1908), while Bushnell was played in a recent BBC drama by Doctor Who (Matt Smith).
Don't mention the Falklands at the Olympic Park hockey centre today, where Britain's men are taking on Argentina. GB's heady victory in the 1988 Olympics ("Where were the Germans?" asked commentator Barry Davies as the final goal flew in, adding " Frankly, who cares?") seems a long time ago now: the men haven't medalled since, although the women did pick up a bronze in 1992. The men's hockey was once the sole preserve of India - they won six straight golds between 1928 and 1956, were upset by Pakistan in the 1960 final, then won again in Tokyo in '64. It's said that India's superiority was eroded when artificial pitches became commonplace, making it, almost literally, a more level playing field.