What happened at the Emirates? Arsenal's home game dominated by Cologne fans
Arsenal beat Cologne 3-1 in their first Europa League group game at the Emirates on Thursday but the headlines were all about what happened before the match.
The game was postponed by an hour (until 9.05 p.m. BST) due to crowd safety concerns. Thousands of seats designated for home fans were occupied by German fans all around the stadium -- especially in the Clock End.
UEFA and Arsenal are both set to investigate the incident and how so many away fans gained access to the stadium. But here is a short summary of the evening.
So what happened before the match and why was it delayed?
Cologne had been allocated less than 3,000 tickets for this match, but an estimated 20,000 away fans showed up.
That led to chaos outside the stadium as the German supporters blocked home fans from getting to the turnstiles. Eventually, police, UEFA and the clubs agreed that the safest option was still to go ahead with the game.
How did so many German fans get in the home section?
That's the big question that needs to be sorted out. Clearly, thousands of Cologne supporters had been able to purchase tickets that were only on sale to club members. But Arsene Wenger said after the game the club weren't sure exactly how that happened.
"I don't know how they managed to infiltrate our fans and get everywhere. But they did that very well," Wenger said. "I don't know, did they go through Arsenal membership, or the internet?"
Some were undoubtedly supplied by touts, but it seems likely that plenty of Arsenal members also sold their tickets on to German fans.
There have even been reports that Cologne members applied for Arsenal membership as soon as the draw came out, so they could buy tickets from the club website. However, Arsenal say they took measures to stop that.
Was it violent? How many arrests were there?
Given the circumstances, the atmosphere remained largely peaceful and orderly throughout the evening. Video footage on social media showed some German fans kicking down barriers in order to get closer to the stadium, but only five Cologne fans were arrested.
There were some ugly scenes inside the stadium as well as some fans who had tickets for the home section tried to enter the designated away seats and scuffled with stewards.
More flares lit by Cologne fans after they take the lead. pic.twitter.com/nKz9gUmaNI— Mattias Karén (@MattiasKaren) September 14, 2017
Riot police was quickly called in, but there were no major incidents once the game started. A couple of flares were lit but it soon became clear that the boisterous Cologne fans were there to enjoy their first European game in 25 years -- not to start fights.
Metropolitan Police issued a statement after the match saying there were "no reports of any significant incidents. Five people have been arrested on suspicion of public order offences."
What can Arsenal do to stop it happening again?
The most obvious answer seems to be to allocate more away tickets for these types of games. The 3,000 tickets were in line with UEFA requirements, but Arsenal were well aware of the massive interest in this game among Cologne fans -- and the lukewarm interest among the club's own supporters.
In early FA Cup rounds, Arsenal have sometimes allocated the maximum 15 percent of seats -- 9,000 at the Emirates -- to away supporters. Had they sold the same number here, some of the problems may have been avoided.
Several of the other issues seem to be outside the club's control, however. They can't prevent Arsenal fans from selling their tickets on to others, and the consensus seems to be that the club and police handled the situation very well once it arose.
The blame will largely fall on Cologne, who failed to discourage their fans from travelling.
Oh and there was a football match too, right? What happened there?
Arsenal staged a second-half comeback to win 3-1. Cologne actually took the lead after just nine minutes through Jhon Cordoba's spectacular long-range lob, sending the away fans into an even bigger frenzy.
But the Gunners roared back after the break as Sead Kolasinac equalised with a thumping volley and Alexis Sanchez scored with a superb curling strike to give the hosts the lead.
Hector Bellerin added the third goal, but not even that could silence the German fans, who kept serenading their team well after the final whistle.
Mattias is ESPN FC's Arsenal correspondent. Follow him on Twitter: @MattiasKaren.