It was the chairman's idea.

How could he get the NFL, one of the largest global brands in all of sports, to agree to hold regular-season games in a Premier League stadium? It had never been done.

Maybe the NFL thought Tottenham Hotspur chairman Daniel Levy was, as he said, "a little bit mad" in 2012 when he suggested the two agree to hold NFL games in his club's new 61,000-seat stadium beginning when it opens in 2018. But the NFL listened.

Levy proposed equipping the stadium with a retractable pitch -- a grass soccer field over a synthetic surface for NFL games -- which would make it possible to hold two games in the same stadium on the same day. Over time, Levy also agreed to configure the stadium so the sight lines would be as good for NFL games as they would be for soccer games and to build a dedicated NFL-sized locker room and NFL-sized medical and media facilities.

"We worked together," Levy said, "because it needed to be viewed as a combined joint soccer and NFL stadium. In fact, the way we designed the whole experience is one side of the stadium is a dedicated soccer entrance and the other side is a dedicated NFL entrance.

"If it ever got to a stage where the NFL decided it wanted to have a permanent team in London, this stadium could literally be, whatever the team was, it would be their stadium as opposed to an NFL team feeling they're renting Tottenham's stadium."

That is a big reason why Mark Waller, the NFL's executive vice president of international, told ESPN.com earlier this year that he could see the league putting a team in London by 2020 "if the ownership decided that was something we wanted to do."

The NFL has been building a fan base in England since it started its International Series there in 2007. The league has held 14 regular-season games in London -- all at Wembley Stadium -- and will hold three more there this season, including one at Twickenham Stadium, home of England's national rugby team.

Tottenham chairman Daniel Levy consulted with the NFL when planning for his club's new stadium. "As we sat down and we went through all the operations," he said, "we worked out, 'What does the NFL need? What does soccer need?'" Clive Rose/Getty Images

Starting in 2018, the NFL will hold at least two games at Tottenham's as-yet-named stadium for a 10-year period, although Levy said, "We've encouraged them to engage with us in a wider way."

If the NFL decides it wants to base a team in London, Levy said the Spurs would like to host it.

"We would welcome very much close cooperation with the NFL and a dedicated team," Levy said. "Obviously a decision is entirely theirs whether they do bring a team to the U.K., and where it would be located is something that would be talked about. But yes, we would be very much welcome to that scenario."

When Levy became chairman for the Spurs in 2001, he had three objectives: improve the quality of the team, build a world-class training facility and build a new stadium.

When the stadium, which will be adjacent to Tottenham's current White Hart Lane home, is complete, Levy will have achieved all three. Last season, the Spurs finished third in the Premier League, their highest finish of Levy's tenure. And a couple of years ago they moved to a new training facility, where they soon will break ground on an addition for player housing.

But the stadium and the accompanying neighborhood revitalization project -- both of which are known as the Northumberland Development Project -- are Levy's baby. The project includes the construction of new homes, a hotel, a medical facility and a grocery store, among other things.

"I have lived and breathed this project from day one," the 54-year-old Levy said. "It is absolutely my ambition to make this work. When I first started talking about it internally at the club, again I think people around me thought I was mad as well. I guess it's my tenacity to get it done because there were many times with the NFL where there wasn't going to be an arrangement. We just kept going back and saying, 'What about this? What about that?'

"When we first went to them, we went to them with the idea of a joint stadium in some shape or form without going through all the details at that stage. As we sat down and we went through all the operations, we worked out, 'What does the NFL need? What does soccer need?' Basically we had a checklist of all the various things we wanted to achieve, and then at the end of the day it was the best solution."

Levy said he researched stadiums in the United States, and while he said he didn't want to "give away any trade secrets," the major difference between venues there versus in England is the scale. "They're enormous," Levy said. So while Tottenham's video boards will be the largest in a European stadium, they won't touch the size of some in the U.S.

Fourteen NFL games have been played in London, all at Wembley Stadium, a venue built primarily for soccer. AP Photo/Sang Tan

And although Levy looked at the retractable grass field at University of Phoenix Stadium in Glendale, Arizona, home of the Cardinals, there were logistical differences there, too. That field retracts outside the indoor stadium, where it can be exposed to sunlight. At the Tottenham site, where land is at a premium, the grass field will retract under the stands and be exposed to artificial light.

But unlike Wembley Stadium, the Spurs' new venue won't need to be reconfigured to accommodate an NFL field. So the turnaround time from hosting a soccer match on the grass field to an NFL game on the synthetic surface will be two hours.

"One of the idle thoughts we have at the moment is, would you really be able to play an NFL game and an EPL game on the same day as a doubleheader?" Waller said. "It wouldn't be absolutely out of the question. I don't think you'd want to do it on a regular basis, but on a unique feature, that might be a really interesting idea."

Said Levy: "I don't think it's something we'd want to try our first game, but that is certainly realistic. How exciting the idea of having the two biggest leagues in the world from a television perspective -- fantastic! -- play on the same day."

While the NFL likes to cite a string of statistics that shows how well it is trending in England -- such as that it has sold out every game at Wembley -- Levy is a bit more conservative in his assessment of whether England can support a full-time NFL franchise.

It starts with kids.

"Kids in school in England don't think about NFL," Levy said. "They think about soccer, and to a much, much less extent rugby and cricket. You wouldn't put the NFL in that list at the moment, and therefore one has to be cautious about the timing of the decision and how that is done.

"I think it's possible and I think it can work, otherwise we wouldn't have invested what we've invested in our stadium, and we wouldn't have entered into the arrangement with the NFL. I just think that everyone needs to have their feet on the ground, and just because you sell out three games of 80,000 or 90,000 people [doesn't mean] that a franchise is an automatic success."

Signage outside the Tottenham construction site touts Levy's grand plans for the project, which will include a hotel and other attractions. Arfa Griffiths/West Ham United via Getty Images

One NFC front office executive, speaking on the condition of anonymity, says he worries about issues beyond the size of the fan base. He wonders if commissioner Roger Goodell and the league are being overly aggressive with their overseas ambitions during a time when player safety is being emphasized.

"I would say 2020 is probably the realistic goal in Roger's mind and the owners' minds," he said. "There's been so much talk about international. My biggest concern is we're trying so hard to go international in so many places too fast that too many bad things can happen. They're talking about playing in China. Are you kidding me? It's a bad idea. There are enormous questions about London that haven't been answered, but it's 'player safety, player safety, player safety.' "

Regardless of the timeframe, Levy emphasized two things would help put a U.K. franchise in position to succeed. One is the continued engagement of fans, young and old. The other is ensuring that the stadium experience is "a real NFL experience," because if it's not, not only will the fans attending the game know it, so will the ones watching on television.

Tottenham is committed to making the stadium experience special, and if and when the NFL is ready to move a team to London, it will be waiting.

"Clearly we wouldn't both be putting all this into this stadium if there wasn't the prospect of one day a team eventually coming to London," Levy said. "But there are certainly no guarantees that A) a team comes to London, and B) they have to use our stadium.

"I think we're all putting the effort in in the hopes that they will do it."