Back in the 1990s, when the National Football League was a nonfactor in the United Kingdom’s sports landscape, Scotland resident Martin MacPherson relied on mail-order newsletters and email lists to communicate with the scattered membership of “Beardown UK,” his Chicago Bears fan club. Decades later, the NFL’s presence in the U.K. has grown from a novelty to a fixture, with sellout crowds packing London’s Wembley Stadium for the league’s annual three-game showcase.

“It’s a real event. The 80-odd-thousand in attendance aren’t just from London, they’re from all over the U.K.,” said MacPherson, who lives in Inverness and travels to London for NFL games. “They recognize big players and respond accordingly.”

The NFL bolstered its future international presence this week with its announcement of a deal to play two annual regular season games at the Tottenham Hotspur’s new multi-sport stadium in London through 2028 -- a step optimists hailed as a precursor to a permanent NFL franchise in the U.K. But experts said it will be several years before the NFL can adequately address the many obstacles an overseas relocation would pose. Travel logistics, tax laws and the realities of the league's revenue-sharing financial model stand in the way.

The International Series has been an undeniable success. Established in 2007 after the failure of the NFL Europe developmental league, the NFL started with one London game per season and gradually expanded to three, all held at the city’s massive Wembley Stadium. Last year, all three of the NFL’s games in London were sold out, with crowds in excess of 80,000.

But Wembley Stadium was designed for use by traditional soccer teams, not 53-man NFL rosters complete with a cadre of coaches and mountains of equipment. The new 10-year deal with Tottenham Hotspur will grant the NFL access to the English Premier League club’s state-of-the-art, 61,000-seat arena. Due to open in 2018, the arena will boast facilities specifically designed for American football, including an artificial-surface field separate from the soccer pitch. Boris Johnson, the mayor of London, was upfront about what city officials have in store for the arrangement.

“Touchdowns in Tottenham can only add to our reputation as a global sporting powerhouse, and help us take another step towards our goal of having a permanent NFL franchise here in London,” Johnson said in a press release.

The Tottenham deal doesn’t spell the end of the NFL’s time at Wembley, though. The league confirmed it plans to extend its agreement with that stadium’s officials when it expires in 2016, meaning the NFL could play an unprecedented five games in London across two stadiums in 2018, Sports Business Daily reported.

“The increase in games certainly goes a long way toward solidifying that fan interest, which they believe is there,” said David Carter, executive director of the Sports Business Institute at the University of Southern California. “They’re at the point now where they’re beyond sticking their toe in the water. They’re really trying to figure out how to position the league so that, if and when a team does end up there, it will be an immediate success.”

The prospect of an untapped market of American football fans has both NFL executives and London officials salivating. A 2013 study by accounting firm Deloitte found that a permanent NFL franchise would inject £102 million, or about $156 million, into the country’s economy, the BBC reported.

The NFL Europe struggled through the 1990s and failed in the early 2000s because fans wanted to see the league’s true stars, not a developmental league with subpar competition. The International Series brought real NFL teams overseas, and fans in the U.K. have responded. There were 13 million American football fans in the country, more than 3 million of whom consider themselves die-hards, the NFL estimated this week.

An increasing number of these fans attend U.K. colleges and universities, where officials have seen a groundswell of interest in American football. The British Universities & Colleges Sport officially recognized American football as a sport in 2012. In just three years, dozens of universities have created their own teams. College-age individuals, as well as American expats living in the United Kingdom, play a crucial role in the sport’s long-term prospects overseas, said John Brewer, a professor of sport science at St. Mary’s University in Twickenham, a town near London.

“All of them are going to want to watch what is effectively their national sport, but do that alongside Brits who are getting equally enthused and interested by the sport,” said Brewer, a British Universities & Colleges Sport board member who recently advised U.K. Parliament members on the sport’s promotion. “Our country has evolved and changed, and I think it is much more ready to accept American football than it was 20 or 30 years ago.”

This new interest – and the revenue it could generate – would seem like an enticing proposition to an NFL owner. But an actual relocation to the U.K. wouldn’t simply be a matter of booking a flight and watching a bank account fill up.

Some of the obstacles are obvious. The NFL would have to establish a schedule that would accommodate a London-based team’s cross-Atlantic travel on a weekly basis. It would be nearly impossible for an NFL team to play a Sunday night game in Kansas City, then travel to London in time for a Thursday night battle the following week. The relocated team would also face the difficult prospect of convincing high-profile free agents to uproot their lives in the United States to play in a European city.

And while the NFL would collectively benefit from an increased overseas fan base, it would be difficult for league officials to convince one of its 32 owners that a team in London would be any more lucrative than a team in an average American city. The NFL’s revenue-sharing arrangement equally divides profits amongst all franchises, regardless of their location. Television deals apply league-wide – individual teams can’t secure their own deals.

Ticket sales from home games provide just a small portion of a team’s income. The real money comes from stadium naming rights, personal seat licenses and in-stadium advertising – none of which would be on the table in a Tottenham-owned stadium.

“For any individual team owner, there’s absolutely no reason to want to be there,” said Neil deMause, a New York-based sports stadium financing expert and co-author of the 1999 book “Field of Schemes,” which analyzed the economic effects of sports stadium deals.

The NFL would also have to navigate a quagmire of legal issues, such as the U.K.’s tax regulations and labor laws, said Kristi Dosh, a Florida-based sports business expert who has contributed to ESPN and Bleacher Report. London-based players would be subject to higher income tax rates than their compatriots, which could affect free-agent signings and create problems with the NFL Players Association. The U.K. Treasury could grant an exemption, but there’s no guarantee. The U.K. would also require American-born NFL players to obtain work visas, a complicated matter for any individual, especially those with criminal records.

In short, an overseas relocation would be a logistical nightmare, even if both the NFL and the U.K. were game. “I just don’t see it. I don’t see how the NFL could make it happen,” Dosh said.

The NFL’s deal with Tottenham Hotspur ensured that the league’s handful of International Series games will be held at a beautiful stadium through the end of the next decade. The U.K.’s budding NFL fan base will likely have to wait at least that long to root for their own team.

“I think we’re talking, at the earliest, a decade or two down the road,” said deMause, the sports stadium financing expert. “It’s not something that’s going to happen anytime soon.”