In January 1998, Thorpe had become the youngest ever swimmer to win a World Championships gold medal when he sensationally beat his fellow Australian Grant Hackett in the 400 metres freestyle in Perth, Western Australia, aged 15 years and three months.

Thorpe was four weeks short of his 16th birthday when he won four Commonwealth Games gold medals that September, all in freestyle races, to complete a remarkable year.

His phenomenal ability was so well-known in Australia that even before that Commonwealth Games performance he drew a stream of accolades from coaches and swimming legends.

It all helped him to earn several lucrative sponsorship deals before he was 16, and Thorpe made sure that one of those deals, with the airline Qantas, would help him to make the Kuala Lumpur Games special for his young friend Michael Williams too - despite the fact that Michael had just undergone chemotherapy.

Thorpe, helped by his agent, organised for Qantas to fly Michael and his family to Malaysia so he could cheer on his friend and hero.

The two boys played computer games, watched films together, and had a special bond. It was Michael's time in hospital - where he underwent six months of treatment before eventually recovering - that helped Thorpe to overcome a malaise of his own before he started breaking world records and winning a stream of gold medals at the Olympic Games, World Championships and Commonwealth Games.

Michael, whose elder brother David would marry Thorpe's sister Christina, had been close to death when he was diagnosed with non-Hodgkin's lymphoma at the age of 13.

A large tumour was removed from his gut, and he was on life support when Thorpe first visited him in hospital.

At that time Thorpe had lost his keenness for swimming. He felt unmotivated and wondered whether the 4.30am starts were really worth it. As he revealed years later, Thorpe struggled with depression throughout his teenage years.

Seeing Michael in hospital changed Thorpe. "I came to realise what was wrong, that my talent was a gift and that I'd started questioning it, expecting too much of it," he would say later.

"What I saw because of Michael was how precious life is, how important it is to love what you do, every day. It changed my life, opened my eyes to the world. When I was feeling in pain in workouts I'd start thinking 'this is nothing. Michael's feeling much more.'"

Thorpe would visit sick children in other wards too. 

Not only did he set up Michael's all-expenses-paid trip to Kuala Lumpur, he arranged for some of the biggest names in Australian sport to visit Michael too. This included Kieren Perkins and Dawn Fraser from swimming, the Waugh brothers from cricket and David Campese from rugby union.

When, in 1999, Thorpe won a AUD$16,000 bonus for breaking a world record, he donated it to children's cancer research and a youth crisis prevention programme.

By the time of his second and last Commonwealth Games appearance, in Manchester in 2002, Thorpe was a triple Olympic champion.

He won a remarkable six gold medals in Manchester, the 100m, 200m and 400m freestyle and three relays, and was second in the 100m backstroke.

But the mental health issues returned, and in the build-up to Melbourne 2006, Thorpe was drained and unable to compete. He withdrew a week before the start, and announced his retirement from swimming later that year at the age of 24.

In interviews within the past two years, he has said he regrets that decision but he had been unable to cope with the pressure and expectations heaped on him.

He later needed treatment for alcohol abuse, but, like Michael, he eventually recovered.

In an interview in 2020, Thorpe said: "I only ever aspired to be content in what I was doing, and then there was a point where I realised - 'you know what, I'm actually happy'.

"I can still experience the emotions and the elation that I'm so happy in my own skin."