The 71-year-old – who competed in the single scull at the 1968 and 1972 Games, at Mexico City and Munich respectively – was hospitalised and placed on a ventilator after contracting the virus.
Speaking to ITV’s Good Morning Britain back at his home, Dwan said: “I had that oxygen mask on. I’m breathing 100 per cent oxygen and my mindset went back to Mexico City.
“And prior to Mexico City, I had to do some training on bikes and treadmills with oxygen on. I thought, if I’m going to win this race, this is part of the preparation, and I could put up with this.”
Dwan was close to tears as he recalled the moment he was allowed to leave hospital.
He added: “When they push you round the corridors and you come through all those zip-up air chambers and I could see the double doors at the end of the corridor, and as we got closer it opened.
“I went out into the sunlight, went into the fresh air and it was so emotional. Even now. I’d come back to life and I’d come back to my children and my grandchildren.
“My little granddaughter is four and she wrote a letter to Father Christmas. She said: ‘Father Christmas, I don’t want any presents this year, my sister doesn’t want any chocolate buttons any more. All we want is our granddad home’.”