“I thought: ‘Oh my God. Román Torres. Look where you are, mate. This is it.’” There were three minutes left in Panama’s final World Cup qualifier against Costa Rica when the centre-back went forward one last time. It was an emergency, a moment of desperation, and yet there was method in the madness. Sitting in sector 131 of the Estadio Rommel Fernández, one man probably knew that better than anybody, although he could never have imagined this.

When the ball dropped and Torres burst through to score, 32,000 Panamanians in the stadium erupted. So did he – and he, like Panama’s opponents on Sunday, is English. For Gary Stempel, there from the very beginning, this was the culmination of a long journey for all of them.

“That day was like a release,” Stempel recalls. “You know what they have been through, you’ve seen the sacrifices, the pitches they’ve played on, without proper equipment, with no boots; street kids with the remote, distant dream that one day maybe they’ll play football.”

Torres was one of hundreds of young hopefuls who showed up at trials organised by Stempel. When he asked who was a striker, a couple of hundred hands went up. Torres was a striker but he didn’t much like those odds, so he kept his arm down. When Stempel asked for midfielders, 150 or so responded. Still too many. Again, Torres waited, not raising his hand until Stempel asked for defenders. One in seventy‑or-so were odds he liked a little more. More than 25 years later, the forward who became a defender went back up front and took Panama to the World Cup for the first time. It is not just Torres; it is virtually all of them. “Gary is one of the main people in this film,” says Gabriel Gómez, the central midfielder who has won more Panama caps than anyone.

Stempel was born in Panama, has a Panamanian passport and his father was a professional baseball player. How, then, did he get into football instead? “Well, I went to England,” he shoots back, grinning. Now 60, he went, aged six, with his English mother. He lived in north London, went to university in Aston, did a physical education course at Sheffield and worked for Camden council until 1985 when he saw an advert for a community officer at Millwall FC. Eventually, encouraged by his father, he moved back to Panama. In 2009, he ended up as coach of the national team.

Stempel had set up soccer schools, trying to build a football in the community programme, and coached at US bases. He became manager of Panamá Viejo – and won the league. From there he worked with the Panamanian Football Federation, running trials and coaching, finding and developing kids. He took the Under-20s to the United Arab Emirates in 2003 – the first time any Panamanian team had been to a World Cup – and worked with the U17s, whom he currently manages. When he took over the senior side, he led them to the 2009 edition of what is now the Copa Centroamericana. It became the first tournament Panama ever won.

Along the way, he brought through many of those players facing England in Nizhny Novgorod. “He is one of the people who most helped Panamanian football,” says the coach Hernán Darío Gómez, known as El Bolillo. The nation’s president, Juan Carlos Varela, says: “Profe Bolillo is closing an era, but this was built on the efforts of many men, especially Gary and the Dely Valdés brothers.”.

The striker Blas Pérez says: “Gary was our first coach; he opened the doors to us at a very different moment in Panamanian football history and gave us knowledge. His management was phenomenal.” The defender Felipe Baloy adds: “We’re here because of him.”

Stempel says he is usually described as “paternalist”, his role as much pastoral as about play. He looked after them, often kids from difficult backgrounds, paying for them to get to training, giving them food, teaching them. “He educated us: more than anything else; he guided us,” Pérez says. Baloy says: “He taught us to be better people, to behave.”

Stempel recalls: “Millwall prepares you for most things in life but nothing prepares you for that. You have to improvise every day. The facilities were terrible: a small primary school pitch, holes everywhere, no nets. We didn’t have a cooler so we used a bucket, which we filled at the church next door. Sometimes they would turn up and sometimes they wouldn’t. They got no expenses so some couldn’t afford to travel. We’d play skins v shirts because there was no kit. And this was the national team, you know.”

Gómez says: “Gary got hold of us very young. We barely had any resources. He told us to make the effort, that he could see a lot of talent, not to give up. He gave us the chance to play at under-17 level, under-20 – the first World Cup – under-21, the full team. It was Gary who discovered us and made us who we are. He educated us, off the pitch too, gave us a different mentality: however bad the situation, we could overcome it.”

“A lot of us were at risk socially,” Gómez continues. “He would go to deprived neighbourhoods, look for players, help them. He was a father to us. A lot of us had very little; we couldn’t get to training, there wasn’t enough to eat. He would call: ‘What do you need?’ A teammate’s wife got pregnant and Gary helped with the baby. He had that in his heart. He treated us like sons and he saved a lot of us from falling into things that would have taken us from football. He was there at the start and he gave us what we needed on the pitch, but he also gave us principles.”

“I remember very clearly that Gary used to say to us: ‘At the end of it all, you’ll realise that it was worth it.’ And it was worth it.”