A look at the 10 must-see events at London 2012.
1. Usain Bolt v Yohan Blake (100m and 200m sprints)
The fastest man the world has seen - the greatest title in sport - against the man who would be king. The battles for the 100m and 200m will be the most eagerly awaited contests of the Games. The line-up for both races will almost certainly be the quickest ever seen, but it is the duel between the two Jamaicans that may well come to define London 2012. Bolt is the one with it all to lose. The defending 100m and 200m champion and world record-holder in both has shown signs of being human after all since his stunningly brilliant double triumph in Beijing. He is not the form runner: that is Blake, his younger training partner. The 22-year-old, the youngest man to run inside 10 seconds and the youngest-ever world 100m champion, beat Bolt twice in the Jamaican trials. Bolt has fitness concerns, too, but it takes a brave man to write off a genuine sporting great.
2. Michael Phelps v Ryan Lochte (swimming)
Another quest to depose the king. Phelps is the greatest Olympian the pool has ever seen and will remain so whatever happens in London - from where he certainly will not return empty-handed.
What is also certain is that he will not match his phenomenal deeds of Beijing - where he claimed eight gold medals - to add to the six from Athens. He is only - only - going for seven this time, but in his way is the late blooming Lochte. The 27-year-old already has three Olympic golds to his name and will be competing in a third Games. The previous two have been in Phelps's shadow, but he enjoyed a better World Championships than Phelps in Shanghai last year. Honours finished just about even in the US trials but the Olympics is all about peaking at the right moment and that is what Phelps is extraordinarily adept at.
3. Mark Cavendish v Peter Sagan (men's cycle road race)
This may not reach the heights of Bolt v Blake or Phelps v Lochte, but it is a duel that could determine the direction the Games take for a medal-hungry home nation. Four years ago Nicole Cooke emerged from the rain to win road-race gold and set Britain en route for their most successful games for a century. The men's road race will hurtle around Surrey and then down the Mall mid-afternoon on the first day of the Games. If all goes according to plan it will deliver a first gold of the London Olympics for Britain. Cavendish famously came back from Beijing as the only member of the track team not to win a medal. This time he is on the road and an Olympic gold is his priority, the Manxman having shed weight and sacrificed Tour de France ambitions to improve his chances. Sagan and his Slovakian team are his likeliest challengers. The 22-year-old impressed in his debut Tour - Dave Brailsford, the Team Sky principal, compared watching Sagan to seeing Lionel Messi play soccer - but Cavendish has the experience and the superior support team.
4. Great Britain v Australia (all events)
The sports ministers of the old sporting enemies have a bet on this battle - whichever country finishes lower in the medal table (decided on number of golds) will see the respective minister face a forfeit. Expect, then, to find Kate Lundy rowing the Olympic course in a GB shirt. Britain should win the overall contest but there are some intriguing head-to-heads across the sports. The best should come in the velodrome in the men's and women's team pursuits. The British women, Dani King, Laura Trott and Joanna Rowsell, are the world champions and the world record-holders, the men are the world champions - and the Australians are the only ones likely to have a chance of stopping either. Day one of the Games sees Britain's first Olympic basketball team take on Australia and that will only end one way - Australian victory. But one win won't make a green-and-gold Games.
5. Jessica Ennis v Nataliya Dobrynska (heptathlon)
The face of the London Olympics finally gets to compete in her first Games. Injury denied Ennis the chance at Beijing so it has been a long wait for the 26-year-old - she won her first major pentathlon title in the 2006 Commonwealth Games. In her absence in 2008 Dobrynska took gold and is back - and, most importantly, back in form after a rocky couple of years. Tatyna Chernova, the Russian world champion, is sure to be in contention, but it is the Briton and the Ukrainian who are the outstanding athletes in the field. Dobrynska is four years older but appears to be running, jumping and throwing better than ever having set a new indoor record in winning the World Championships in Istanbul ahead of Ennis earlier this year. But Ennis has beaten her before, at both the 2010 World and European Championships. Her form is encouraging, too, having set a new British record in May.
6. China v United States (to top the medal table)
The contest to top the medal table is unsurprisingly a two-horse race. In Beijing the US collected 107 medals, China 100 and next best was Russia a distant third with 73. It was China who topped the table with their haul of 51 gold medals - a comfortable margin clear of the US, who collected 36. China had the significant advantage of home soil - which given their size of population was always going to lead to a greater home surge than other hosts - and whether they can maintain that advantage over the US in London will be one of the themes of the Games. Carl Lewis, for one, believes London will prove a home from home for the US, given many athletes' familiarity with the capital and the language and cultural similarities. China's rise to sporting superstardom has been dramatic - in 1988 they finished 11th equal with Britain with five golds. They will take some shifting.
7. Spain v United States (basketball)
This is America's medal, the one that every team is expected to bring home. Only once, in 2004, has the US failed to win gold (they did not compete in 1980) and this time there are suggestions Stateside that the latest batch, headlined by Kobe Bryant and LeBron James, could be better than the 1992 Dream Team. No way, says Charles Barkley (possibly because he was a pillar of the Dream Team). Barkley goes even further in pushing Spain's chances of producing a shock. Spain are the European champions and reached the final in Beijing. They are also confident and a their players say they can improve on 2008. As Argentina demonstrated in Athens, hoop dreams do not have to belong to the US.
8. Victoria Pendleton v Anna Meares (cycle sprint)
This not only has the Britain v Australia factor, it's also got a hefty dollop of enmity too. The queen of the British track team has not spoken to her Antipodean counterpart for six years - since Meares crashed into Pendleton at a World Championships. "She likes to push the rules. I don't," said Pendleton. Pendleton is approaching the last lap of an illustrious career but is still capable of defending the gold she denied Meares in the sprint four years ago. Since then Meares, now 28, has had the better of the head-to-heads - until the World Championships in Melbourne. They met in the semifinal and it proved as dramatic a confrontation as ever. Pendleton fell after a collision; Meares was disqualified for going outside her lane; Pendleton won the decider in a photo-finish and went on to win gold in the final.
9. Louis Smith v Krisztian Berki (gymnastics)
Britain has never won a gymnastic gold medal at the Olympics and will never have a better chance to do so than via Smith, who won a bronze in Beijing. But even more than in most sports at this rarefied level, the margins between success and utter failure are tiny. Smith (below) is a bold performer on the pommel horse, an athlete at his peak. But he is also an athlete who has only once won a gold medal at a major championships, and that was the Commonwealth Games. Smith performs the toughest routine in the world - the gamble will be whether to use it. If he does and gets it right, the gold will be his. If it goes wrong he will struggle to medal at all. Berki has acknowledged that if Smith clicks his chances are slim, but the Hungarian is the consistent one, as golds from the last two World Championships demonstrate.
10. Rebecca Adlington v Federica Pellegrini (800m, 400m freestyle)
Adlington came from nowhere to win double gold in Beijing. She will not be taking anyone by surprise this time and will have to deal with the pressure of being one of the host nation's big hopes. The 800m freestyle is hers to lose - her form is excellent - but the 400m should be much closer. Pellegrini, the first woman to break the four-minute barrier, is favourite. She beat an under-prepared Adlington at the World Championships last year. The Briton's preparations have, though, been impressive, and with her post-Beijing wobble behind her, her ability to produce when it matters will make her hard to beat.