Is it any wonder the crackle and swell surrounding an NFL franchise in London continues to strengthen, like a storm gathering pace over the Atlantic? Even among the route-one medallion rock of Def Leppard, the warm-up act to Sunday night’s muscular encounter between the Miami Dolphins and Oakland Raiders, you could hear the money being accumulated, measured and treasured.

The 83,436 crowd at Wembley paid an average of around £100 a head. It is a staggering figure but full-house signs are also expected when the NFL returns to the UK late next month and again in early November. That’s close to 250,000 people and £25m in gate receipts. With the rumour mill suggesting there could be five games in Britain soon, a permanent London team no longer seems preposterous. But it still feels deeply premature.

Let us say this though: even the NFL didn’t expect the International Series in London to be this successful, or to sharply accelerate in popularity from a solitary mid-season visit between 2007 and 2012 to three this year. Yet the audiences – a mixture of the hardcore, the corporate and the curious – continue to grow: a sort of sporting version of Parkinson’s law of data, where the numbers expand to fit the space available.

And the crowds are not flocking to the American football equivalent of Chelsea v Manchester City. Miami against Oakland was more like Hull City v Burnley, at least in terms of rank and reputation, and none of the six teams playing in London in 2014 made the play-offs last season.

Can you imagine any other sport – apart from British-bred football – filling Wembley three times in short succession with middle or lower-tier sides? The NFL’s boldness is being well rewarded.

So when the Dallas owner, Jerry Jones, reckons a London franchise is “going to get done”, and the Dolphins quarterback Ryan Tannehill suggests “where there’s a will, there’s a way”, it is tempting to believe they are accurately reading the NFL’s futures market.

Ryan Tannehill, the Miami Dolphins’ quarterback, believes there could be a London franchise as the will to create one is there. Photograph: Tom Szczerbowski/Getty Images

There is certainly the will – as the Premier League has shown, a vast global brand is a license to print TV revenue money – but is there really a way? It is not only about the leap from three to eight games a London franchise would entail, but the resulting logistical and operational nightmare.

The obvious starting point is America is a long way from London. Seattle, for instance, is nearly 4,800 miles from Heathrow – almost the same distance as Beijing (5,055 miles). It is tough enough for 53 players and a team’s staff to acclimatise flying coast-to-coast across America. Regular long-haul would be even harder.

True, a London-based team could play a block of two or three matches at home, then base themselves in the US for a similar chunk of time. But would a player want to spend weeks away from his family – rather than the odd night or two? Probably not. Recruiting experienced players would surely be harder and more expensive.

For a London team to have a greater chance of success it might require a larger salary cap, which would not be universally popular among the other 31 NFL owners. The alternative – low audiences at Wembley to watch the Monarchs (or Jaguars or Rams) being defenestrated – would be even more damaging to the game’s expansion.

And that’s assuming Wembley was available. England play home international matches in the autumn. Can you imagine the furore if the national pitch was duffed up by an NFL match and an England player twisted his knee?

When I spoke to George Atallah, a senior figure in the NFL’s powerful players’ union, he pointed out other potential areas of contention relating to health and safety and players’ working conditions. The UK’s higher rates of tax could be a thorny issue too.

His organisation was not opposed to a UK franchise, Atallah stressed but he pointed out “a permanent team in London would require collective bargaining between the league and the players’ union and the NFL have not got to the point where they have raised it”.

There is a bigger problem – and I say this as someone who spent many Sunday evenings in the 1980s listening to the NFL on Armed Forces radio, trying to pick out an American accent between scratchy white noise and blasts of Wagner: the sport has yet to infiltrate the mainstream as it did back then.

Sky’s coverage of the NFL has not yet made the top 20 most-viewed list for satellite TV this season, whereas lower league games such as Burton Albion v Portsmouth (watched by 138,000 viewers) and repeats of Friends and the Royle Family have. Most British people would not be able to name a single current NFL player.

It might change, given time and broader TV exposure. Certainly the NFL’s aim of becoming the UK’s third biggest sport is not overly outlandish but the steady approach – more British fixtures over time, coupled with a first game somewhere like Berlin – may be the more sensible play before a full-blown London franchise gets the go-ahead.

But this suggests the NFL is deeply considering the riskier option. And Hail Mary’s sometimes come off.