"You would be puffing and panting just walking up steps," he recalled as he sat in the office of his boatyard at Eel Pie Island, slap bang in the middle of the River Thames at Twickenham. 

"And when you got to do your pieces, you were fighting to get air in."

Earlier this month this 71-year-old Londoner endured a similar and far more lengthy experience as he fought for his life in an intensive care unit after contracting coronavirus.

Last week the happy result of that struggle became widely known as he was interviewed on ITV's Good Morning Britain show after getting back home. His story transcends national borders.

The gaunt figure on the screen was very different from the broad and powerful person who had spoken of his time as a "very angry young man", fighting for the right to become the first person to reach Olympic rowing from the Docklands.

When I spoke again to Dwan yesterday, this time on the phone, he explained that he had lost three stone during the three weeks he spent in hospital and now weighs just over 14 stone – exactly his old racing weight.

He acknowledged the irony of the Mexico Games experience – and added further detail to his assertion that his survival had been significantly assisted by his experience as an Olympic competitor. 

He also added a new credit to the singer Helen Shapiro, who had a million-selling British and US number one hit in 1961 with "Walkin' Back to Happiness".

"It's funny how it's come back 50 years later," he told me as he sat enjoying the sunshine in the back garden of his home in Bexley, Kent. 

"I needed to draw on the same experience. God was on my side this time – and how much that experience that pulled me through. The old memories came back – Olympic preparation, you know.

"I'm not a competitive person any more. After I'd finished rowing it didn't matter. But the minute I put that oxygen mask on the competitive instinct came back.

"I remember an old coach used to say to me 'it's money in the bank'. 

"Every time you put that little bit of money in the bank, when you need it, you can draw on it. And that's what I felt.

"However fit I am, I could get a little bit fitter, and a little bit fitter, and some day I'm going to need to draw on that little bit.

"I am so lucky. When I went in there they had me on 100 per cent oxygen for five days. And I wasn't responding to it. And they did phone my wife up and told her 'we are going to turn the oxygen off'.

"It was very, very touch and go."

So did he put his survival down to his "athlete mentality"?

"Completely," he said. "When I was laying in that ward without that oxygen mask on, you know, you can see and hear things. There were people ripping their masks off and dying in front of me. Talking to their loved ones, and then hanging the phone up and 10 minutes later going out in a body bag. That wasn't nice.

"So my mindset went back to 'well, that ain't for me. I'm not ready for that'. And I thought to myself, well, before we went to Mexico City for the Olympics we did a training session.

"They put us in a room and they changed the air to as if we were at 10,000 feet above sea level. And then they made us do an hour's circuit. They would also wire me up and give me a mask and put me on a bike or a treadmill.

"My mindset went back to – this oxygen mask is just like that preparation. My mindset went into the fact that this is part of the training for a race. And if I'm going to do any good in this race I've got to put up with what they are doing to me.

"And whilst this mask is strapped to your face, you can't move your face to left or right, you can't lift your head off the pillow, and I felt right, well, whilst I've got this mask on this is part of the training.

"I thought, 'I've got to run up a hill' – I used to do training in Greenwich Park – and I thought, 'I've got to run up this hill, and walk back down it'. I would go ten hours running up a hill in my mind and walking down a hill.

"I said to my wife, it came back to me the other day, all the time I was doing it I was singing to myself an old Helen Shapiro song – Walkin' Back to Happiness. And then I would come off the mask for a couple of hours and that was my rest period.

"And all the way through, that's all I was thinking – 'if I'm going to get through to this race, then this is what I've got to do.' And I'm sure that helped me through. The words of the song are also, 'walk away from loneliness'. And that was so apt, really. Because I wasn't going to go backwards, I was only going forwards. And it was going forwards into happiness.

"So as soon as that mask went on, that song helped me up the hill and back again. Why that song – I don't know. I quite like it – but it ain't a song I would put on if I had a shilling to put in the juke box!

"Anyway, God was on my side, and he let me through…"

Dwan, who had treatment for leukaemia three years ago, added that another turning point was the decision to give him steroids. A further irony, given the way in which his competitive years – he finished sixth and last in the 1968 Mexico Games final and failed to qualify from his semi-final at the 1972 Munich Olympics – were effectively impacted by the illegal and covert pharmacological assistance offered to many of his rivals.

"When I was sculling we were green as grass," he recalled. "We just weren't prepared in the proper way. Especially against the Russians and the East Germans and all of the other eastern-bloc countries.

"They were on all sorts of things, you know. I'm so pleased now that they are getting this drug situation right. Because it was such an unfair playing field.

"The minute I went onto steroids the oxygen levels came down and down. But even on the Saturday before I came out of hospital last Monday I couldn't walk, couldn't get out of the bed. They said until you get off the oxygen you ain't going home, so I said 'well look, turn the oxygen off and let's see what happens. Just keep an eye on me'.

"I went an hour without it. I went two hours without it. And then went through the night without it. And gradually, gradually, slowly, slowly I was able to get my legs out the bed.

"I had these two old men in the ward. And every single hour – they were ever so determined to get home – they got out of bed and walked up and down. And I thought 'if they can do it, I've got to do it'.

"So on the first day I did 50 step-ups, and the next day I did 60, and I just built it up like that, until the Monday when they came round and they said, unless you can walk you can't go home. And I managed to walk round the ward and down the hallway. And they let me home.

"Having pneumonia and the amount of oxygen they were putting into me has damaged my lungs. But they are recovering very quickly.

"When I first come home from hospital – as I said in that thing on television the other day – when they pushed me out of that hospital and the doors opened, and I went into daylight, it was like being born again.

"It's so lovely to be home. With my family. I can walk. When I came home I could probably do about 10 steps. Then I had to sit down to get my breath back again. But everything is on the right way up rather than on the wrong way at the moment.

"The other day my wife put the shower on for me, and I had enough breath to get into the shower and stand under the water and she said to me 'you gonna use some soap?' And I said 'that will come later in the week'.

"This morning I could stand at the mirror, and I can actually now put soap on my body and wash myself off before I lose my breath again.

"I've got to learn how to do it again. And the greatest thing that's happening to me at the moment is the lockdown - because it's forcing me to take it easy. I get up, I have my breakfast, I read the paper. I sit in the chair. I have a sleep. I think it's the greatest thing out.

"Whilst I was in hospital there were two things I promised him up above. One, I would give up alcohol. And the other thing was I'm retiring.

"I promised him up there that if he let me go, I would do it. And I've never gone back on a promise.

"I've got about an acre of ground here and I managed to walk half the length of the garden yesterday. I'll have another go today - go and smell the flowers."