After the Lions failed on their two-point conversion and trailed, 21-19, with less than four minutes left, the Falcons looked to have the game in their hands.
With a 21-0 halftime lead, Atlanta looked to be in firm control. Even through the comeback, the Falcons needed just a couple of first downs to be able to run out the clock and get the win at Wembley Stadium.
But a couple of critical errors in the final minutes helped give the Lions enough of a window to get a last-second field goal and a 22-21 win.
"I'm very disappointed in the way that we played in the second half of the football game. You can't make the mistakes that we made in the second half against a good football team," Falcons coach Mike Smith said, "because when you do, they're going to come back and haunt you. They did."
On the Falcons' last drive, they had a critical holding penalty on Nathan Stupar on a second-down running play. The Lions declined the penalty on the 1-yard loss, but the officials had to stop the clock to sort out the play.
"We had some very untimely penalties. We did some very uncharacteristic things on both sides of the ball," Smith said. "You can't give up the big play like we gave up, and you've got to keep the ball in your possession."
On the next play, the Falcons looked like they were going to put the game away but Julio Jones dropped a pass from Matt Ryan. If the Falcons had called another running play, the clock would have continued to run.
Those two plays left enough time on the clock for the Lions to execute their final drive and kick the winning field goal.
"It was third-and-10, just trying to make a play, just trying to do too much in that situation," said Jones, who had four catches for 58 yards. "I should have just caught the ball and just went down. Even if I didn't gain a yard, we still could have ran some time off the clock."
Ryan blamed the offense for not executing on the final drive, opening an opportunity for the Lions to be able to come back.
"On second down, obviously with a penalty, the clock doesn't continue to run. That makes it tough," Ryan said. "And then on third down we have a pass play called, and then in those situations we've got to execute, I've got to execute and make sure that it's a completion so that clock continues to run.
"I think across the board, we feel like we gave them too much time and kind of didn't do our job. Offensively we did not do our job."
After that series the Falcons had to punt, but the Lions still had to drive about 60 yards in the final two minutes to set up a field-goal try. Atlanta's defense couldn't hold them, giving up a 32-yard pass to Golden Tate on the first play and another 20-yard catch by Theo Riddick two plays later.
As the Lions were frantically working their way down the field, Smith called a timeout with 25 seconds left, stopping the clock and giving the Lions a chance to regroup and figure out their strategy.
Another Falcons penalty for defensive holding helped set the Lions up on the Falcons' 30, making a potential 48-yard field goal a little closer.
After a delay-of-game penalty negated Matt Prater's missed attempt, the Lions capitalized on the final play, with Prater hitting the winner from 48 yards, completing the comeback.