Minutes later, he found himself astride a mountain bike with an oversized helmet strapped to his head, lined up at the starting line with a dozen other children. Some were proudly decked out in fancy jerseys, Lycra shorts and Gore-Tex gloves, other were nervously looking around to check out the competition. The young Choi, however, seemed untouched by the excitement, and simply waited quietly for the starting whistle.

Despite having no race experience except for challenging his father on the cycle path, he finished third in the four-lap race.

His parents were not overly impressed at the time. But now Choi Chun-wah, a construction company manager, and his wife, Chan Suk-yee, are looking forward to seeing their son compete against the world's best in the Men's Omnium event in London. A cycling version of the decathlon, it comprises six races over two consecutive days, starting on August 4.

'We did not see that coming,' his mother says. Her son hadn't shown any particular interest in cycling in the past, although he was always an active child.

'He had enrolled in surfing, tennis, and other sports programmes in the previous summers, but there wasn't one that had to do with cycling.'

That early success brought an invitation to sign up for a three-stage programme to nurture future sports stars. He made the first cut, began formal training at the Hong Kong Sports Institute just as he was about to enter secondary school, and hasn't looked back since.

Inevitably, the demands of elite sports training encroached on his studies. By the time he was in Form Three, there was barely a free moment.

School took up most of the day, after which came hours of road training. When he finally got home, there were private tutorials to guide him through the plethora of assignments and help him catch up with his classmates.

Chan, a housewife, recalls how they dealt with her son's increasingly punishing schedule.

'At first the training took place just three to four days per week, but very soon it became almost daily. There were also so many competitions, local and overseas, that he had to skip days of classes.

'He was so tired that sometimes he would fall asleep at his desk with a book in his hands, but he never ever uttered a word of complaint.

'His teachers liked him because he always handed in his homework despite the overwhelming schedule. He's a tough kid.'

At 14, he already revealed the ambition and single-mindedness that became crucial factors in his success. Chan says she will never forget how her son came to her one night with his plans.

'He said, 'Mum, I have thought about it. I really like cycling and I am good at it. If I continue cycling I am confident that I will become something great. Even if I study like everyone else, graduate and wear a suit to work in an office, it wouldn't mean anything to me if I'm not enjoying what I do'.'

The speech made a deep impression on his parents. Although they initially hoped he would do well in school and take a more conventional career path, both backed Choi wholeheartedly when he chose to become a full-time athlete after completing Form Five.

At his old school, Po Leung Kuk Wu Chung College, where Choi's achievements constantly feature on its website, principal Chan Yuk-kai recalls his impression of their first Olympian.

'He found his passion, his strength, and set his target early; then he worked very hard towards it. He never complained,' principal Chan says.

Teachers gave Choi the space to pursue his goal, he adds, but Choi's endurance and ability were the most important factors in his success.

Even so, Choi and his parents faced many tough questions along the way. For instance, should he compete in the 2008 Asian Cycling Championships, which would require travelling to Japan just before the start of the Hong Kong Certificate of Education Examination series? While most students might spend months revising for the public exams, the race would leave him with just three days to prepare after his return.

But it was a rare opportunity and his coach, Dorming Chau, had high expectations of a medal win, so his parents gave the go-ahead.

Choi didn't disappoint: he won a silver medal in the junior individual road race, a Hong Kong triumph surpassed only by veteran cyclist Wong Kam-po, who took gold in the same category in 1991. When the exams ended, Choi became a full-time cyclist, going on to represent Hong Kong at major international races.

His ever-expanding trophy rack at home is testimony to his progress and an even more gruelling regimen (up to 10 hours daily, combining sprints, distance and weights) that has taken him away to the mainland and other parts of the world for months at a time.

'Every time I sent him off for training I couldn't help but cry,' Chan says. 'At one point he was away for so long I took part-time jobs to distract myself from how much I was missing him.'

Choi is grateful for his parents' unwavering support behind the scenes, recalling how his father often rose before dawn to ferry him to races.

'They did not force me on which path I should take. Instead, they listened and gave me the best support,' he says.

'They would get up at four in the morning for my competitions, which often start in the early morning, and came to see me race whenever they could.'

With barely two weeks left before the biggest milestone in his cycling career so far, Choi is putting greater emphasis on strengthening the upper body muscles which aid his acceleration.

Choi's parents won't be in London to cheer him on at his Olympic debut because the tickets had been sold out by the time their son was confirmed as a competitor. But as far as he is concerned, they will be helping to power him on wherever they are.

The boy whom head coach Shen Jin-kang describes as someone who 'speaks little, works hard' is determined to make it a joyful challenge.