“The perception of me is that, basically, I am a madman,” James McClean says calmly. “I’m outspoken. I’m a loudmouth. I’m very opinionated and I hate all things British. That’s from people who don’t know me. The reality is quite the opposite. I’m pretty boring. I go training, go home and switch off. A lot of my days are quite bland, quite basic.”

McClean sounds as sane as he looks gaunt on a bleak Monday in Derry. He spent 14 years in English football and the fact that he is now at war with his own club, Derry City, can’t obscure the fact that he is the fifth-most-capped Republic of Ireland international, having played 103 times. “People define success in different ways,” he says, “but I’m the only footballer from the north of Ireland to win over 100 caps for Ireland. I played 150 Premier League games over five seasons, 800 professional games and won a lot of individual accolades. I count that as success and don’t look back with regrets.”

But there’s sadness, too, in the way his life and career were scarred by his refusal to wear the poppy when playing games around Remembrance Sunday in England. “It’s completely changed me as a person,” McClean says. “It’s made me a bit of a recluse because I don’t trust a lot of people now. I’ve been stung bad.”

McClean’s autobiography, The Walls, is one of the best sports books of the year. It’s a powerful and sometimes disturbing read elevated by McClean’s willingness to show himself in an unflattering light.

I have written a lot about Derry and boxing, and Bloody Sunday, but it helps to be back here to understand how McClean can respect the millions of soldiers who died in two world wars while refusing to forget how the British army killed so many Irish people in this city.

He comes from Creggan, the estate affected most on Bloody Sunday in 1972 when 14 unarmed civilians were killed by the British army in Derry. Six of the fatalities were from Creggan. In 2010, after the Saville report finally concluded that all the victims posed no threat, the British prime minister David Cameron apologised for the “unjustified and unjustifiable” massacre.

McClean was born in Derry in 1989 and he writes that “learning how to make a petrol bomb was one of my first life lessons. I was 11 before I’d properly mastered it.”

He pauses when asked how he would feel if any of his three daughters or his son, who is 11, ended up making petrol bombs. “I’m very thankful they don’t have to. It’s a different era now. I just want them to be proud to be Irish.”

The 37-year-old spells out the contrast with his youth. “I grew up in a very Republican community still dealing with the effects of the Troubles. You would see gunmen on the street. People got shot, kneecapped. To get access to my street you had to go through a lane where you sometimes saw masked men doing punishment beatings. But you weren’t scared. You knew you’d done nothing wrong. That was the norm … but it’s not normal.”

His biological father, Joe Kelly, was an alcoholic in Creggan and McClean spoke to him only once – when he shouted at him in the street to stay away. But he remembers a happy childhood and, when his professional career began with Derry City, “I was very carefree”.

McClean was 22 when Steve Bruce signed him for Sunderland in August 2011. He made his Premier League debut that December after Bruce was replaced by Martin O’Neill. McClean soon became a regular starter and that first season in English football was full of joy and praise. He was fast, skilful and disciplined. Apart from wasting money his biggest vice was typing his name on Twitter where he would revel in glowing reports of his play.

“It was amazing,” McClean says. “I never thought about the politics when I first got to England so up until November 2012, when the poppy thing started, I never experienced any bother.”

Everything changed when he told Sunderland he wouldn’t wear the poppy because it also represented the British army which had occupied Derry for so long. “There was never a decision for me to make,” he says. “Wearing the poppy was just never going to happen. It was a very difficult year and I felt a lot of that could have been handled better by the club. But Sunderland came out with a statement before the game which drew all eyes on me. It was there to protect the club. They basically said this is James’s personal decision but we, as a club, wholeheartedly support the poppy appeal.

“I wanted to make my own statement but I was constantly told by the club that: ‘No, no, it’ll die over. Just leave it.’ I’d just turned 23 and I thought the club had a duty of care to look after me and that’s what they were doing. I’d won the player of the year the previous season but I felt they hung me out to dry.”

McClean recalls that: “The next game was away to Fulham on a Sunday, on Sky. A threat was made that I would be shot if I came on to the pitch. I remember [his wife] Erin panicking. It sounds extreme and people might say: ‘Oh, wise up, you’re not going to be shot on TV.’ But the night before the game I was assigned two police officers to stand outside my door. So the Met police took it seriously and that made it more real.”

O’Neill brought him on in the second half and his every touch was booed – by the Fulham and Sunderland supporters. The vitriol poisoned his world but McClean kept searching for his name on Twitter. He became furious whenever, after a mutually respectful encounter with a member of the public, the person would go online to abuse him.

Sometimes McClean would track the person down and demand an apology. “Maybe that madness was always there, but it got stronger,” he notes.

McClean moved to Wigan before joining West Brom where, in “the best kind of madness” he earned £42,000 a week while he had his best spell in the Premier League. But as one poppy season blurred into another, the death threats kept coming, as did the warnings that Erin would be raped. McClean says: “My reaction was always to fight fire with fire. I went into some games in the wrong frame of mind. It wasn’t: ‘Can I help the team?’ It was: ‘I hope I score today so I can shush them up.’”

McClean admits: “There were days where I went looking for the conflict.” He posted a photograph of himself listening to his favourite Wolfe Tones song, The Broad Black Brimmer. “I knew exactly what I was doing,” McClean writes. “It was an IRA song – and I was sure it would rile a certain type of person up.”

By the time he reached Stoke, for whom he played 111 games between 2018 and 2021, his problems in English football reached a new low. “Brexit made the idiots louder” and “the poppy season seemed to be getting longer every year”. He had also made a stupid mistake during lockdown when he posted a photograph of himself, wearing a balaclava, with his two eldest children below a caption which read: ‘Today’s school lesson – History.’”

McClean thought he was being funny but his choice not to wear the poppy, in contrast, was heartfelt. “I thought others might have followed suit but it never turned out to be the case.”

Did he feel that a more rounded understating of his stance had emerged by the time he enjoyed his happiest seasons in English football, while playing for a Hollywood-tinged Wrexham from 2023 to earlier this year? “A wee bit, aye. When you explain it to footballers you’ve played with, and to people on a personal level, it opens their eyes and they say: ‘Oh, I understand that.’ But the overall British population? I don’t think so.”

Reflecting on his Premier League years, McClean marvels at the brilliance of Kevin De Bruyne and Eden Hazard. “You had to accept there were lads capable of doing things that were beyond you,” McClean writes. “But there were also games where I thought I was coming up against a physical strength that I found suspicious. Coming back into the Premier League after a break convinced me that some players had to be benefiting from some kind of performance-enhancing support.

“I remember coming up against one player that I’d encountered at Sunderland who I always felt that I’d been able to match in terms of his speed and power. While I’d been away from the Premier League, he’d gone to a bigger club, and now he was a different animal completely.”

These are startling allegations and, while McClean has no concrete evidence to support his doubts, he trusts his gut reaction. “I’ve always been very fanatical about my fitness,” he says. “But when you come against the top Premier League clubs, no matter what height, what size, they’re just faster, they’re stronger, and you’re thinking: ‘How is that possible?’”

After their daughter Willow was diagnosed with global development delay and autism, Erin persuaded him to be tested for autism. He was found to be “at the high-functioning end of the spectrum” but he still struggles with the fact that “I’ve probably got body dysmorphia or some kind of bulimia. Maybe it’s the autism thing, because I’m so strict with my diet 95% of the time. But when I can’t work out I binge. So if I’m travelling and flying, I’ll just eat that much shite to the point where I have to make myself sick. I still feel really guilty, because the next day I’ll punish myself in the gym – which is not healthy.”

Life has become even more complicated since he returned to Derry City in January. “I was meant to be coming home for the fairytale ending. But you quickly realise the promises are just bullshit.”

McClean has not played for the club since July and, asked about the situation, he says: “It’s not good. It’s a player against owner and there’s only one winner. I think that’s it in terms of Derry City. You never think you’ll be betrayed by your own so it’s painful.”

When contacted by the Guardian, a spokesman for Derry City said: “The club cannot speak to, or comment on, how James feels.” He also rejected the suggestion that Derry City had failed to fulfil any promises made to McClean.

Earlier this month, McClean said he couldn’t “understand or accept” the way he was being treated by the club and that he was fit to play despite being left out of the squad by interim manager Mark Connolly. Derry City then released a statement in which they said: “The club has sought to resolve this internal matter privately. Out of respect for confidentiality and the fact that this dispute involves sensitive medical details regarding James’ hip condition, the club have previously refrained from making any public statement on the matter.”

McClean insists he could play football elsewhere but how does he feel if this is the end of his career? “It doesn’t unsettle me because I’ve been boxing off and on for 10 years and in the past 18 months I’ve really thrown myself into it. I’m not going to start a pro boxing career because it’s just not feasible at my age. But I’ve been in contact with Misfits and they want me to fight.”

Misfits Boxing was set up by KSI and the Sauerland brothers, who made their name in the traditional fight game, and it features YouTubers and former athletes who want to become boxers. It is dismissed by boxing purists but McClean sounds enthusiastic about making his debut in the ring once his contract with Derry expires: “Boxing is giving me that purpose to wake up and train hard.”

What kind of boxer would he like to become? “I’m a pressure fighter. I like to be constantly in someone’s face because I’ve got the fitness to maintain that. I’m not saying I’m by any stretch of the imagination a [Gennady] Golovkin or a Canelo [Álvarez], but I love watching them. I’m not looking to have a career in boxing but three or four fights a year is perfect. The dream was always to be a footballer but this is a new excitement, a new challenge.”

As we prepare to step out into a rain-sodden Derry, there seems little chance of any reconciliation for him on the football field. But he looks up and his taut fighter’s face suddenly relaxes into a smile. “It could be a blessing,” McClean says softly. “It could end up a blessing in disguise.”