This article originally appeared on VICE Sports UK.
"You know how to get a British crowd on your side?" I ask a group of Kansas City Chiefs fans, all American, "Just go behind early – we always cheer for the underdogs and the comeback."
"The Chiefs are good at that!" says Erica, who grew up watching the team at Arrowhead Stadium before moving to Amsterdam.
Along with Erica and her friend are Cheryl and William Dawson, who have flown all the way from Kansas City to see their beloved Chiefs in action in London. They aren't alone in following their team across the Atlantic; there are huge groups of traveling American fans all around Wembley.
"I came over for the game," says Jason, a Detroit Lions fan dressed head to toe in a white and blue Lucha Libre outfit "It's a unique experience and I wanted to travel and check out the sights. This is just an addition to it."
His outfit catches the attention of a big group of Lions fans who are posing for pictures beside one of the Wembley signs.
"First time in London. Love it. Love the city, it's old, it's just great. History, just everywhere you go," says Derek, one of the more vocal members of the group.
Seeing as he's a man that knows how to be loud, I ask him about whether he thinks Kansas City giving up their home game –and the raucous crowd found at Arrowhead –would be an advantage for the Lions.
"The Wembley crowd will step up. I think it'll be about even, though, even though Kansas City are the home team. It'll be about even."
Having stadium noise be about even would be a big advantage for the Lions. The Chiefs are giving up a lot by coming to London for a home game, but losing the 12th man effect is the biggest; the noise that hometown crowds bring isn't just encouragement for the team, it plays a big tactical role. When the home team are trying to set up their attacks, the crowd is pin-drop silent to allow all the instructions to go out. When the away team are on the march, the home fans let all hell break loose, making as much noise as they can to disrupt whatever is trying to be accomplished on the field.
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It's serious business. The Seattle Seahawks' fans, for example, have been so noisy that they've shown up as an earthquake in the Pacific Ocean.
That's why it's key for the Chiefs to get the Wembley crowd firmly behind them if they're to recapture the advantage lost by playing in the capital instead of their own stadium. It's not easy, as Wembley is renowned for having a bipartisan crowd.
"Everyone wears just any American jersey," says Chiefs fan Erica, not quite getting to grips with the British mentality, "it's freaking me out! It's like, if I have anything American, I'm just going to wear it and go."
"It's really funny, because I can't imagine showing up at a Manchester United game wearing a Tottenham jersey if they were playing Chelsea!" she adds.
By the looks of things before the game, the Wembley crowd are at their neutral best. The sea of jerseys is out in full force, as are a fair few not wearing any teams' colours. One group, though, stands out –a gaggle of Green Bay Packers fans in full garb, including a Cheesehead hat. They're all from the UK and Irish Packers fan group, and are catching up after not seeing each other since their annual pilgrimage to Lambeau Field, the Packers' home ground.
They're also all here to cheer on the Kansas City Chiefs.
"The Arrowhead stadium is loud, but we'll do our part," says Phil, "we're noisy."
The Lions are in the Packers' division, and so a loss for the Detroit team will boost Green Bay's chances of reaching the playoffs. They're here to help the nearby UK branch of the Kansas City Chiefs' fan club make Wembley feel a little bit more like Arrowhead. The group knows what it takes to transform Wembley, as they've been to every London game so far.
"It was a little bit tentative that first year," Phil says, "and the weather conditions didn't really help either as it was very wet, the turf was a little too short, and we didn't really know what we were doing at that stage. I think as the years have gone on we've really gotten into it."
Getting the fickle Wembley crowd on their side would be key for the Chiefs. As the designated home team they get to control the in-stadium messages telling the crowd to 'Get Loud' for them, and have kindly put a flag on everybody's seat. As the game kicks off, they do as predicted and try to enamour themselves to the London crowd by promptly going down 0-3 to a Lions field goal.
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Then something quite strange happens. Kansas City score, again and again. They intercept struggling Lions quarterback Matt Stafford a couple of times and take full advantage, going in at the half 24-3 up. It's honestly brutal; the Lions can't get out of first gear, and Chiefs quarterback Alex Smith is tearing them up by scrambling out of the pocket for huge gains. Previously unknown Charcandrick West, stepping into the Chiefs backfield to replace their injured star running back Jamaal Charles, is fast becoming a fan favourite thanks to his bruising runs down the field.
What was truly remarkable was that at no time did the fans get back behind the Lions and cheer them on for the comeback. It didn't even matter than in wide receiver Calvin 'Megatron' Johnson, the Lions had the most famous and talented megastar on the pitch. There were still Wembley moments (such as the fans going from being as disruptive to the Lions' offense as possible to applauding when Johnson stretched out to catch a ball he had no right getting close to) but this was firmly a Chiefs crowd. As the score crept up the fans didn't get disinterested, or try to swing momentum back to the Lions, but instead started baying for blood. For the first time I've seen, the Wembley crowd wasn't bipartisan; Chiefs Nation had arrived in London.
It was a watershed moment for the NFL in the UK; it all clicked into place at Wembley, and the British crowd evolved into a proper American one.
At the first NFL game to be staged at Wembley in 2007, the crowd acted like they were watching a game of cricket; polite while the players set up, and then appropriate applause based on how the play turned out. Now, eight years and 14 games later, they were a full-on American Football crowd, begging for no mercy as the Chiefs piled on the misery for the floundering Lions.
"I don't know why [that happened]," says a fan on the train home after the game, "it's normally a case of cheering on the underdog, or not necessarily the person who's giving you the flags... I can't put my finger on it."
Perhaps it was the Chiefs' sheer dominance, which made it obvious that a comeback wasn't happening, so the only thing to cheer for was a blowout. Maybe it was just the right combination of free flags, cheerleaders, and the T-shirt cannons which were deployed during the longer breaks. It could well have been the combination of traveling American fans and Brits from the domestic supporter clubs which influenced the neutrals within the crowd to get behind the Chiefs. Either way, with the NFL expanding out of its friendly Wembley home and into Twickenham and the new Tottenham Hotspur stadium in the future, this game will be the blueprint for how teams can engage with fans there too.
There are still a lot of issues that come with flying across an ocean to play a game of American football: the time difference, reduced practice time, and trying to keep a sense of familiarity in a country apparently so alien that the New York Jets decided to bring their own bog roll. The Chiefs, though, proved that losing home advantage doesn't need to be one of them after they achieved what many thought was impossible: turning a British crowd decidedly American.