The British diver’s huge profile, coupled to the sheer difficulty of winning gold in a sport dominated by China, had already made his 10m platform victory alongside diving partner Matty Lee one of the most memorable wins of the Games.
But now Daley has revealed in his new book 'Coming Up for Air: What I Learned from Sport' that he also had to battle a life-threatening case of COVID-19 just months before the event began.
The episode, which he decided to keep secret, saw him hospitalised fearing that he ‘might die’, and adds an extra layer of significance onto his incredible achievement in Japan.
“My lungs felt pressurised, as if they had sacks of rice around them. I needed to get to that test centre and find out. I walked there very, very slowly, diligently avoiding everyone I could,” he detailed on the pages of his book, which is being serialised in The Times.
Tom Daley: 'I was really terrified'
When the British diving ace’s oxygen levels started falling, he was taken to hospital by ambulance, where he was hooked up to an oxygen tank and taken to tests before being allowed to return home after 10 hours.
Discussing the ordeal, Daley said: “I understood how quickly things could potentially go downhill. I had flashes of fear about whether I would be put on a ventilator, and my time being up. I was really terrified.”
Three days later, he started to feel better, feeling an 'overwhelming' sense of 'relief' that the ordeal was over.
At the Olympics, Daley put all his previous problems aside to produce the performance of a lifetime.
He and Matty Lee became Great Britain’s first gold medallists in men’s synchronised 10m diving.
It was a first gold medal for Daley in his fourth Olympics, while Lee achieved the accolade in his first.
"To finally have this gold medal ... I’ve been diving for 20 years, it’s my fourth Olympic Games," Daley said afterwards.
"Lots of people would have counted me out, being the older person, but I’m in the best shape physically.
"I still can't honestly believe what is happening," he added. "That moment, being about to be announced as Olympic champions, I was gone. I was blubbering."