ARSENAL'S Europa League encounter with Cologne finally got under way an hour late despite police dealing with "disorder" at the Emirates Stadium as German fans occupied home sections of the ground.
It then took Arsenal 45 minutes to get started.
But after heading to the half-time break down 1-0 thanks to a brilliant finish from 35 metres out from Jhon Andres Cordoba, punishing David Ospina for a clearance that saw him stranded off his line, Arsene Wenger's side rallied in the second term in a game rife with wonderful goals.
Substitute Sead Kolasinac thumped home a volley to draw proceedings level, before Alexis Sanchez produced a moment of sheer magic to remind the home faithful he will still produce the goods despite wanting away in the summer transfer window.
The Chilean, who had a sluggish first half, cut in from the near touchline and somehow curled an unstoppable shot into the far corner.
Hector Bellerin put the game beyond doubt, finishing a sharp move that involved Kolasinac, Theo Walcott and Jack Wilshere, back in an Arsenal shirt.
"We went to four at the back at half-time and the second half was better," Arsenal manager Wenger said.
"Kolasinac makes quick decisions, he's strong in the tackle and quick going forward. He's settled in quickly and we're very pleased to have him."
Thousands of ticketless supporters of German club Cologne arrived at the Emirates, while travelling supporters who did have tickets were unable to gain access to the ground for the Group H opener, with kick-off delayed by an hour in the interests of "crowd safety".
The match did begin at its rescheduled time of 9.05pm local time, having been pushed back an hour from its original 8.05pm start.
A pre-match statement issued by London's Metropolitan Police said: "Officers are dealing with disorder at the Emirates Stadium where fans have gathered for the Arsenal vs FC Koln match.
"A policing plan is in place for the game. Additional officers have been deployed."
One social media post appeared to indicate scuffles inside the ground, with Richard Conway, a BBC sports news correspondent, tweeting: "Koln (Cologne) fans fighting with stewards inside Emirates Stadium. Group arrived in home end and fought their way into away section."
Earlier reports suggested as many as 20,000 Cologne fans had gathered in London just hours before kick-off despite only 3000 tickets being made available to away supporters.