“Long before Tyson Fury was the People’s Champion, I was the People’s Tenor,” says Russell Watson with a wry smile. Comparisons between Watson, a Salford-born classical singer, and Fury, a world heavyweight champion boxer of traveller descent, might at first seem odd. But both rose from humble backgrounds to become among the most successful in their field, and both fought back after battles with their health.

“When I started out 25 years ago I was a bit of a rough diamond,” Watson explains over the phone. “But I have honed my skill over the last 20-odd years or so and I am very pleased where I am at at the moment.”

Watson is speaking from the Cheshire home he shares with his second wife, Louise, and is occasionally interrupted by the youngest and most demanding of their four dogs. In conversation he is liable to spontaneously burst into song and is full of impersonations and amusing anecdotes. The 54-year-old is celebrating two decades since the release of his debut album with the aptly titled 20, an album featuring newly recorded versions of highlights from his career, and a tour in 2021.

Starting out performing in clubs around the North West while working on factory floors, Watson found overnight fame with the release of his debut album The Voice in 2000 and performed privately for figures including Emperor Hirohito of Japan at the Imperial Palace in Tokyo. Nessun Dorma from Puccini’s Turandot soon became his calling card. “I used my own money to get my own vocal coaching and training and did it almost the wrong way round,” he explains. “I learnt as I went along. I started in the industry and I plied my trade and learnt my skill as I was doing it.”

But his career was almost derailed when in 2005 he began having headaches and was diagnosed with a pituitary adenoma the size of two golf balls. He underwent a five-hour operation to have it removed. Two years later he suddenly became incapacitated while recording his album Outside In and doctors discovered a regrowth, which was also successfully removed. So what lessons has he learned in those 20 years?

“You get to the point in your life, especially when you are progressing in your years, and I have been through my fair share of s*** in my life, with ill health and all the rest of it, so I try not to dwell on negativity too much. It’s funny because, back in the early days of my career, I really did used to. A lot of artists will tell you this.

“When I was doing the arenas… you are at the MEN Arena and there are 13,500 people rammed in there and there is one person in the middle with a miserable face not clapping – that is the person you will hone in on.”

Crowning a landmark year, Watson signed up to appear on I’m A Celebrity … Get Me Out Of Here! – which took place in a Welsh castle instead of the Australian jungle due to coronavirus. But this was not a shameless attempt at boosting his public profile (although it hasn’t harmed it). He wanted to test himself. He had repeatedly turned down the show because he thought it would be impossible to keep up his life-saving course of gels, tablets and steroid injections. But, with it moving to within a relative stone’s throw from his Cheshire home, he had no excuse.

Watson arrived at damp, cold Gwrych Castle in North Wales a little after the rest of his campmates, as a surprise, and was fifth to be eliminated. He almost backed out of the Rancid Rotisserie trial, which saw him strapped into a rotating machine that repeatedly dunked him into cold gunge, because it reminded him of the MRI scanner used during his brain tumour treatment. “I’m terrified of small spaces because I associate them with…” he trails off. “I have had so many MRI scans on my brain and various other parts of my body, to be fair, so I am used to having MRI scans, but when I go in it’s like I need a sedative or something to calm me down.

“I have to take my specialist in with me just to keep me calm because I associate those types of things with bad news. So, as a result, I am lying on my back and being strapped into this thing. It was when the bloke who was strapping me in came over, he had his mask on and everything, and it literally felt like I was in a hospital.”

However, there have been some unexpected benefits of appearing on the show. “I’ve dropped a full suit size,” he proclaims proudly.

His health battles have prompted as many headlines as his voice. And he has discussed, at length, the impact his illness has had on his wife and two daughters from his previous marriage. “If nobody mentions it, I am happy not to talk about it,” he admits. “If someone does mention it, I am happy to discuss it as well. If I had a preference I would probably never discuss the thing again. But, inevitably, when I have an interview I get asked the question about it and then I have the conversation.”

He fears his name may have become synonymous with his illness. “One of the things I am concerned about is that sometimes it almost becomes like you are defined by this thing that you have been through, and I am not necessarily sure that is a good thing.”

Despite all this, Watson admits his life story is one worthy of a biopic – singing at the opening ceremony of the Commonwealth Games in 2002, performing in private for Pope John Paul II, being asked by Slash of Guns N’ Roses to join his supergroup. “It’s something, to be fair, that we have been talking about recently,” he says excitedly. “Someone was talking about even turning my career into a film. We are in the early stages of discussing those types of things. The people we were talking to at the time were saying it is like Billy Elliot with bells on.”

20 by Russell Watson is out now. His 20th anniversary tour will now take place in 2021.