She qualified with a herculean performance in Australia in June, covering the 2.4-mile swim, 112-mile bike ride and 26.2 mile run in 10 hours and 47 minutes. But the demands on her did not stop there. Cheng also has to fund her participation, to the tune of HK$80,000 (US$10,000).

Organisers call the race in mystical Kailua-Kona, the town hugging Hawaii’s west coast, “the ultimate test of strength, grit and heart”. Cheng, then, should be right at home.

Cheng “hated sports” as a child, but was placed in swimming lessons by her mum, Liang Weifen, who swam for China at the 1984 Olympic Games.

“I could not see the fun in sport,” Cheng said. “I finished last in any competition and did not like showing myself up. My family never put pressure on me, but I put it on myself.”

Still, Cheng was a natural in the water. “Because of my mum’s genes,” she said, demonstrating a lingering instinct for downplaying her talent.

She tentatively introduced running – “I was out of breath after my first 100m race” – and cycling, and has undergone a transition from bashful, unathletic schoolgirl to elite, role-model athlete.

The undulating process has featured mental adversity, stellar performances, obtaining then losing that cherished job, binge-eating, the establishment of a successful business, and training – lots of training.

Cheng’s professional and athletic lives have been interdependent since she graduated from university.

Her airline ambition was initially thwarted by an industry recruitment freeze. An office job caused stress, and Cheng “did not know what I was achieving, or what my goal was”. She had “mild depression” and quit sport.

Motivation and happiness were progressively restored through an uplifting sequence of events.

She landed her dream role, with Cathay, and finished first for her age group in a half-ironman, which led friends to convince Cheng to commit more time to sport.

Qualification for the 2019 half-ironman World Championship followed, but progress the year after was blown off course by a perfect storm.

Finnair, where Cheng worked for three years after Cathay, made her redundant because of the Covid-19 pandemic. She sustained a debilitating back injury and separated from her boyfriend of six years.

“I had no income, I trained, but with no purpose, because there were no races,” Cheng said.

“I was unhappy and moody. I was binge-eating and gained a lot of weight. I had no confidence and did not want to go out, I did not speak to anyone for two months. That was the darkest period of my life.

“Eventually, I talked to some friends about my feelings and fears and worries. Gradually, I felt better.”

Cheng launched No Limits Coaching, a personal training enterprise, and steadily restarted her own sport. After 18 months, Cheng had the belief and condition to target Kona.

“This has been my dream for 10 years, but I did not dare vocalise it, because it is so hard to achieve,” she said.

Cheng trains for 20 to 24 hours a week, around coaching and overseeing her business.

“I am shattered every day, but I enjoy training … I want to see myself improve,” she said.

An angry scar on Cheng’s knee, the product of a crash at June’s Hong Kong Road Cycling Championships, serves as a vivid reminder of her sport’s inherent dangers.

“Nothing was broken, but it was a deep wound and is still painful,” Cheng said. “Mentally, it was difficult starting to ride outside again, but it is getting better.”

If Cheng’s limb remained in one piece, she is “breaking my bank account” to compete in Hawaii.

The overall HK$80,000 cost includes a HK$12,000 entrance fee and steep travel and accommodation expenses – although Cheng is “hoping for more sponsors”.

“Triathlon taught me to never give up on anything,” she said. “When I am racing, I feel a fire inside me. I want to inspire people.”

Crossing the finishing line – she hopes in less than 11 hours – will almost inevitably prompt an inward vow of “no more”.

“Every time I finish a race, I say I am not doing it again,” Cheng said. “But I will keep going for as long as possible, because this is my life.”