When David Sullivan was growing up in a council house in Cardiff, he dreamed of becoming a professional footballer. Short and squat, he would never be a player, but later in life the fortune he built through the pornography industry and the property world gave him a route into the sport. The only problem, Sullivan discovered, was finding a club willing to roll out the welcome carpet for him and his business partners, David and Ralph Gold.

They were fans of West Ham United and bought a stake in the east London club in 1991, only to find entry to the boardroom closed. “We had no contact with the board,” the late David Gold wrote in his autobiography. “They simply did not want David Sullivan and the Golds at their football club.”

Connections to the world of adult entertainment counted against Sullivan and his associates. Knocked back, they looked elsewhere. They considered moves for Leeds United and Tottenham Hotspur before settling on Birmingham City, who were in administration and struggling in the second tier of English football when they were bought by Sullivan and the Golds for £700,000 in March 1993.

In different circumstances, perhaps this would be the story of how Sullivan defied the blazers who shut him out, about how he took Birmingham out of financial difficulty and eventually became the most powerful man at West Ham.

Instead, it is one with an unsavoury ending, and a tenure which club sources say had become “chaotic” in its final days, culminating in Sullivan’s resignation on Saturday amid accusations of “improper conduct” which Sullivan describes as false, and over which he has threatened to sue the BBC.

Many inside the game will be taking in the news of Sullivan’s departure and reflecting on how a pornographer managed to rise as high in the modern game as he did.

When he bought Birmingham, his first major football club, he was not a mysterious figure. It was well known that Sullivan was convicted of living off immoral earnings from prostitution in 1982 and spent 71 days in prison before a successful appeal led to his release. He was the owner of the Daily Sport and Sunday Sport, the notorious red-top tabloids known for their topless photoshoots and salacious stories.

For Birmingham, financially stricken, those concerns could be overlooked. “How he’s made his money is unimportant,” a reporter said in a news report on the takeover. “His desire for success is the only criteria on which to make a judgment.” That is an assertion which does not appear to have aged well.

As for the authorities, there were no available criteria to block the takeover: the fit-and-proper-person test was not introduced by the Premier League, Football League and the Football Association until 2004 but it is hard to see how Sullivan would have fallen foul of it even if it had existed in 1993. The rule was designed to rule out those with a history of financial malpractice or corruption, not a morally questionable business history.

Now the conversation will shift. His resignation will be a relief to the West Ham fans who have been pining for an end to Sullivan’s 16-year ownership of the club – a desire made all the more acute after last month’s relegation from the Premier League.

People inside West Ham will hope for a clean break. The curiosity with Sullivan, though, is why he has refused to walk away before now. One theory is that football has served to sanitise his reputation after his days in the porn industry – but the truth is he has never become a sympathetic figure. He has been targeted with protests from West Ham fans for the best part of a decade, and often faces harsh criticism from the football media over how he runs the club.

Views on his time at Birmingham are also mixed. Sullivan took the club into the top flight in 2002, where they remained until relegation six years later, but he and David Gold never enjoyed universal popularity. They tired of the criticism. But when they sold to the Hong Kong tycoon, Carson Yeung, in 2009, there was no question of them stepping away from football.

West Ham were in a vulnerable financial state in 2010, and Sullivan saw opportunity in that vulnerability. He and Gold bought the club in January of that year.

His tenure has rarely been smooth. Supporters have never forgiven Sullivan, Gold and Karren Brady, who stepped down as the club’s vice-chair last month, for the opportunistic deal that took West Ham away from Upton Park and into the London Stadium in 2016. Yet Sullivan clung on. He had made plans to buy a portion of the Gold family’s shares. The idea was that he would be an equal partner with another of the club’s shareholders, the Czech billionaire and owner of Royal Mail, Daniel Křetínský.

Sullivan did not accept that modern football had left him behind. He was desperate to win and never seemed more animated than when haggling over a transfer. He has lived through the Premier League boom, and the economic opportunity that has come with it. But while the sale of Birmingham was worth £81.5m, Sullivan can argue that he regularly injects cash into West Ham and that owning a club comes at a personal financial cost.

And unpopular though he is with West Ham fans, there is, indeed, a sense that football has helped to legitimise, if not sanitise him. Sullivan is who the cameras pick out when West Ham are losing. He was on the pitch when they won the Conference League in Prague in 2023. No longer the former porn baron, he appeared instead as one of the Premier League’s ranks of faintly absurd billionaire owners. He seems cartoonish. In its own way, it is a form of sportswashing.

It is impossible to know if there ever was a grand, humanising strategy. This is not a Middle Eastern oil state with a dodgy human rights record buying Manchester City or Newcastle United. It is one man who often made populist moves in attempts to placate supporters, only to end up reviled by his own fanbase.

His final match as the club’s chairman saw him jeered by supporters as West Ham’s relegation was confirmed on the final day of the season. The defining image of his tenure will be of him leaving his seat in the directors’ box early.

In that sense, football has done nothing for Sullivan’s reputation. He will leave a toxic legacy at West Ham. Internally, there had been fears that allegations about his personal life – all of which he has denied – could cause sponsors to walk away.

In recent times Sullivan has cut an increasingly isolated figure. With allies like Brady having distanced themselves professionally from him and accusations swirling, resignation and the threat of legal action appeared to be his last and only option.

As the owner of West Ham, Sullivan lived his dream, leading an institution of English football into what he hoped would be its bright future. Ultimately, it was questions about his past that brought all that to a halt.