It is believed to be in protest of President Donald Trump's comments this week on protests during the anthem.
The Ravens, whose players had never protested during the anthem, had 10 players take a knee: linebackers Terrell Suggs, C.J. Mosley,? Za'Darius Smith,? Tim Williams and Tyus Bowser, wide receiver Mike Wallace, defensive lineman Carl Davis, safety Tony Jefferson, and defensive backs Anthony Levine and Lardarius Webb.
Many of the Jaguars held hands along the sideline, and about 10 took a knee, including cornerbacks Jalen Ramsey and A.J. Bouye, defensive ends Calais Campbell and Yannick Ngakoue, defensive tackle Malik Jackson, safety Tashaun Gipson, and running back Leonard Fournette.
Ravens coach John Harbaugh, Jaguars coach Doug Marrone and Jaguars owner Shad Khan stood with the players during the anthem.
"We recognize our players' influence," Ravens owner Steve Bisciotti said via statement. "We respect their demonstration and support them 100 percent. All voices need to be heard. That's democracy in its highest form."
Khan issued a statement afterward that said, "It was a privilege to stand on the sidelines with the Jacksonville Jaguars today for the playing of the U.S. national anthem at Wembley Stadium.
"I met with our team captains prior to the game to express my support for them, all NFL players and the league following the divisive and contentious remarks made by President Trump, and was honored to be arm in arm with them, their teammates and our coaches during our anthem.
"Our team and the National Football League reflects our nation, with diversity coming in many forms -- race, faith, our views and our goals. We have a lot of work to do, and we can do it, but the comments by the President make it harder. That's why it was important for us, and personally for me, to show the world that even if we may differ at times, we can and should be united in the effort to become better as people and a nation."
The kneeling players stood for the singing of the U.K. national anthem.
Trump on Friday night criticized NFL players who lodge protests during the national anthem.
Speaking at a political rally in Huntsville, Alabama, Trump said: "Wouldn't you love to see one of these NFL owners, when somebody disrespects our flag, to say, 'Get that son of a bitch off the field right now. Out. He's fired! He's fired!"