The NFL came to London on Sunday, so London's football fans brought out their jerseys. All of them.

This was a Steelers-Vikings game, so of course there were plenty of Roethlisberger 7 jerseys and Peterson 28s among the more than 80,000 fans at Wembley Stadium. But without a real tie to either team, many fans went for the next best thing: any NFL jersey.

The...