This Sunday, the San Francisco 49ers travel across the Atlantic Ocean to play their home game against the Denver Broncos at London’s Wembley Stadium. It will be the fourth regular season NFL game to be in the UK since the Miami Dolphins faced the New York Giants in 2007 and the 12th time that an NFL game has been hosted at Wembley.

This could be seen as a sign that American football is making serious in-roads into the heartland of soccer, as Wembley is England’s national stadium. But this is an exaggeration of the facts. The games played in the UK have certainly been a great thing for British NFL fans, but beyond that core group, it’s hard to see that that much has changed. Many see the games as an unwanted distraction.

It would be an excuse to say that the England football team’s struggles on the pitch are purely down to the playing surface, but the continual abuse of what should be hallowed turf by anything from NFL games to car races has meant the grass has had to be re-laid numerous times. The team has never been able to get familiar with a consistent home surface, and so has been denied some of what it means to have home advantage.

At the same time, I’ve always wondered how American fans view these games. The 49ers will play the Broncos once this year, but no local fans will be able to watch that game up close and personal without spending a lot of money.

On the face of things, it seems that the ownership of the team is putting potential financial rewards from additional exposure overseas ahead of the loyalty of local fans.

Even worse, they could be risking on-field success.

In most sports, home advantage has an accepted influence on results. The current table for the English Premier League shows the leaders, Chelsea, to have won all five home games but only two of the four games they’ve played on the road. At the bottom, the three teams sitting in the relegation zone have not won a single game away from home.

Of the three NFL games played at the new Wembley the “home” team has lost twice. The statistics from American bowl games played in the ‘80s and ‘90s disagree with any perceived disadvantage, with seven home wins and one tie, but those were just preseason exhibition games and so for everyone involved they were nowhere near as important.

Last year, the Niners won six and lost two at home, and registered the opposite statistics away, losing six and winning just two. In contrast, the Broncos showed no difference between home and away form, winning four and losing four in both. From this limited analysis, it would seem that by choosing to travel, San Francisco is surrendering its home advantage, and any extra advantage in a 16-game season can make a big difference.

To see if it is a risk to come to London, let’s look at the results we already have in a bit more detail:

In 2009, the Tampa Bay Buccaneers were poor everywhere, so they did not lose much by playing a home game in the UK. The New England Patriots, in comparison, were rock solid at home, winning all eight, but bad on the road. Playing in front of a neutral crowd rather than in Florida might have made the difference that saw them win.

A year before, in 2008, both the New Orleans Saints and San Diego Chargers were better at home than away. The Chargers, though, managed to push the Saints to the wire, clawing back at an early lead to almost upset the home team.

At the inaugural NFL game in 2007 the Miami Dolphins lost at Wembley to the New York Giants in the middle of a disastrous season that saw them win just one game all year, at home. The Giants, in contrast, were almost unstoppable away, their seven wins making up for less-than-perfect results at home to put them on the path to winning the Super Bowl.

With just a sample size of three to base this all on, it is not yet clear if it is a good thing or not to come to Wembley. There may be some indications that the home team is losing some of its natural advantage, but with the Giants’ form in 2007, they would gladly have played away rather than at home.

The sports fan in me is against these games–they seem like the ultimate betrayal of loyal home fans to earn a quick buck, and the concept of home advantage is just too ingrained in my sporting mindset.

The statistician in me, though, demands more data. Sunday sees the last of these games in the current deal between the NFL and Wembley, but several teams are reportedly interested in playing future games in the UK and elsewhere abroad. It may be that the NFL is in London to stay.