Not since 1980 has the opening day of the Olympic Games dawned with such a mixture of anticipation and apprehension.

When the world's largest nation hosts the world's greatest sporting contest, anything could happen - inside the stadium or out. Political tensions and human rights demonstrations have already made headlines, as they did in Moscow 28 years ago. But Beijing's smog, heat, sporting prowess and Chinese patriotic fervour have made these Games among the most political, controversial and unpredictable ever staged. When the last runner in the global marathon relay carries the torch into the Bird's Nest stadium this afternoon to kindle the Olympic flame, he will be watched not only by the kings, presidents and prime ministers of more than 50 countries, by 10,500 athletes and by some 90,000 eager spectators; he will be watched by the world.

For the next two weeks, Beijing will be the focus of hopes, excitement, anxiety and pride in almost every part of the globe. The ferocious competition for medals, records and honour has already sparked spats between tense competitors and rival nations. Britain and Australia are quarrelling over the sporting records, with bets between the ministers and gibes from the press. And already Britain has suffered its first disappointment: the boxer Frankie Gavin, one of Team GB's best hopes for gold, failed to make the weight and was sent home without throwing a punch. Russia, meanwhile, has already disqualified seven of its female athletes for failing drug tests. When the Games begin, these spats have all the potential to develop into full-scale rows and diplomatic incidents, especially if drug testing knocks out high-profile competitors.

Outside the sporting arena, political arguments are already racing apace. A day before arriving, President Bush delivered a speech voicing “firm opposition” to China's detention of dissidents, human rights advocates and religious activists. Mia Farrow, the American actress, is planning to broadcast from a Sudanese camp in Chad on the plight of the Darfur refugees, accusing China of arming and backing the Sudanese Government. Other Darfur campaigners have had their Chinese visas abruptly cancelled. And in Paris the French authorities have caused outrage by banning demonstrations outside the Chinese Embassy planned by press freedom lobbies.

China has, so far, acted with restraint, sensing that an overreaction to criticism or to demonstrations would itself make headlines and be counterproductive. There is no disguising Chinese irritation, however, at what many see as a determined attempt by Western leaders and foreign media to rain on China's parade and dwell on sensitive issues such as the Government's attempts to block websites, the harassment of journalists, the silencing of dissidents and unrest in Tibet and the Xinjiang region. There is a danger of the Chinese perceiving the world as a “bad guest” at their Olympics. Intensely proud of what they see as a glorious national achievement and the symbolic emergence of their nation on the world stage, many people would feel a lasting resentment if outside views were solely negative.

For very many Chinese, the Games will be their first experience of the outside world. Engaging with a formerly closed society can only encourage greater openness and freedom - and this legacy will not be easily suppressed when the Games are over. Equally, it is sobering - and, to many, thrilling - to realise that in 17 days' time all talk of the next Olympics will refer to London. Britain would do well to watch, study and learn from Beijing. Who now can tell what fevered talk will fill the air in London four years from now? But for Beijing the long wait is over. Let the Games begin.