For Aaron Howlett, being chosen as one of the 21,880 people to carry the Olympic flame this year ranks as one of the proudest moments of his life.

“To be asked to carry the Olympic torch is the greatest honour. I’d run it in Iraq,” said the 32-year-old motivational therapist, who lost ten stone (64kg) in 19 weeks to earn the title of the Biggest Loser UK in a weight-loss competition.

Tenzin Dorjee, a Tibetan-American student leader, views the arrival of the flame in London as a different kind of opportunity. He is expecting to be joined by more than 1,000 Tibetans from around Britain and the Continent to converge on the capital to protest about China’s failure to live up to Olympic ideals and the promises it made when it won the Games in 2001.

“London is one of the cultural and economic capitals of the world, so we need to send a message to the Chinese Government that we will not let it spread its propaganda in the free world,” said Mr Dorjee, who was arrested by the Chinese at Everest base camp last year for unfurling a banner in protest at the trial ascent of the torch.

For both, London presents a perfect stage. How the capital responds to the torch’s arrival could have profound consequences for four years’ time when London hosts the 2012 Games.

The arrival of the flame in London marks the first big moment on its 85,000-mile journey through 135 cities around the world in the run-up to the Beijing Games.

The domestic part of its journey takes in the summit of Mount Everest and other parts of Tibet en route to the Olympic stadium for the opening ceremony on August 8.

The relay, the longest in Olympic history, will focus world attention once again on China’s human rights record, with the London leg a potential flashpoint because of its status as the next host city.

Protesters say that the torch, a symbol of peace, justice and brotherhood, should not be allowed to enter Tibet nor reach the top of the world’s highest peak because of the message it would send out. They are calling on the International Olympic Committee and Olympic sponsors such as Coca-Cola to prevent the Chinese from running the torch to the 29,035ft summit, which has been closed to climbers in preparation.

“Taking the torch into Tibet would not only be wrong, it would also be dangerous,” said Kelsang Gope, spokesman for the Tibet Olympic Committee.

Mr Howlett, who will carry the torch in June for Samsung, an Olympic sponsor, in Guilin, in the autonomous region of Guangxi Zhuang, said: “People want to make a statement because there is no higher-profile event than the Olympics, but it’s not the time or the place. The Olympics is about bringing people together.”

Mr Dorjee is expecting to be joined by human rights activists protesting about China’s role in the Darfur crisis.

When he was arrested at base camp last April, he said he and four friends were interrogated by the Chinese police for two days — the first without food. After their release, they were deported. “Some Tibetan people in China are not so lucky,” he said.

Darfur, which prompted the Hollywood director Steven Spielberg to resign as an artistic adviser to the Games, is still an issue for Beijing in its attempt to present the most spectacular and biggest Olympics yet. Activists, led by the actress Mia Farrow, plan protests in San Francisco and Hong Kong, which will receive the torch on April 9 and May 2 respectively, to ensure that Darfur remains on the political agenda.

Beijing officials have refused to allow their plans to be derailed. Jiang Xiaoyu, executive vice-president of the Beijing Olympic Organising Committee, said that the Tibet leg of the relay would proceed as planned and be a “great feat of Olympic history”.

He added: “We heard recently that some organisations are claiming they will stage protests. Those activities will not win the hearts and minds of people and are doomed to fail.”

The route could still be changed if protests turn ugly. Security experts have done a reconnaissance of all the cities hosting the torch and local police forces and governments have to sign a contract promising to ensure the safety of the torch and its bearers. Risks are being constantly assessed.

“It is entirely conceivable that a leg could be cancelled,” said Neil Fergus, a security adviser to the Chinese who has experience of three torch relays.

“We did it for the Sydney Games when the torch was due to go to Fiji but there was a coup. We came close with the Solomon Islands when two militia groups wanted to have their photograph taken with it at a road block. I don’t think this relay is going to get out of hand because it has been meticulously planned.”

The relay was confined to the host nation until the Sydney Games in 2000 when it toured the Asia-Pacific region, but is becoming increasingly important as the Olympics grow in size and commercial value. The Athens organisers were the first to take it all the way around the globe in 2004.

The logistics of the torch relay are complex. Several “mother flames”, which are constantly alight as a representation of the Olympic spirit, are transported in their own specially designed private jets with a core team of security guards. They are then used to light thousands of replica torches carried by celebrities and ordinary people nominated by the host cities and the three sponsors, Coca Cola, Lenovo and Samsung. Beijing’s event starts officially on Monday when the flame will be lit — using a mirror to reflect the Sun’s rays — in Olympia, Greece, the home of the Ancient Games. The torch will be passed to Chinese officials on March 30 who will fly it to Beijing for the start of its journey across the five continents. Its first international stops before London are Almaty in Kazakhstan, Istanbul and St Petersburg.

The IOC said that the route of the torch relay was plotted by Beijing Olympic organisers and could not be dictated by Olympic chiefs in Lausanne. A spokeswoman said: “The IOC shares the world’s desire for a peaceful resolution to the tensions of past days in Tibet. We hope that calm can return to the region as quickly as possible.”

Hope, dreams and TV

— Lighting a flame for the duration of the Games began with the Ancient Greeks. It represents “hope and dreams, sunshine and happiness, friendship, peace and equality”

— It made its first appearance in the modern Olympics at the 1936 Berlin Games overseen by Hitler

— A new model is made for each Games from aluminium. It is fuelled by propane and, when there is no wind, the flame is 25-30cm high and is always bright enough to be seen on TV

— Mother flames, in safety lanterns, are kept alight constantly

— The final torchbearer does a lap of the stadium before lighting the cauldron with the Olympic flame, after which the Games begin officially

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