And with that, I'll leave it. Thanks for your company this afternoon. It's been an afternoon of twists and turns in the Premier League - and at the end of it, Jose Mourinho sits on top of the table. A familiar feeling for him. Will it last? Stay tuned for the next nine months. For now, though, it's goodbye.
- Walcott had penalty saved at 0-0
- Ramsey & Coutinho both off injured
- Mane scores superb individual goal
- Listen to match on BBC Radio 5 live
Very, very early days, but here's how the embryonic Premier League table stands. It won't stay that way for the season, though, surely?
Well, funny you should ask. The leaders on the opening Sunday of last season? Leicester City.
It has been a strange weekend in the Premier League, with last season's top two - Leicester and Arsenal - both losing their opening game. My BBC colleague Chris Bevan has been chasing down the stats gurus at Opta this afternoon to find out the last time that happened. Impressively, they have come up with the answer.
It was in 1953 - and again, Arsenal were involved. The Gunners, then champions, lost 2-0 at West Brom, while runners-up Preston were beaten 2-1 by Huddersfield.
In short, what we've seen this weekend doesn't happen very often.
In today's two EFL matches, meanwhile, QPR when top of the Championship by winning 2-0 at Cardiff, while in League One, Bristol Rovers defeated Oxford 2-1.
Let's bring you up to date with today's other results. In the early kick-off, Manchester United began Premier League life under Jose Mourinho with a 3-1 victory at Bournemouth. Juan Mata, Wayne Rooney and Zlatan Ibrahimovic scored for United, Adam Smith for Bournemouth. Mourinho was content enough with the performance, as he said in the video below when speaking to Match of the Day,
Here's a little more of Wenger, speaking to Sky Sports: "We played a very good first half and were unlucky to concede a goal just before half-time because the free-kick was very harsh.
"After that we paid for a lack of experience. I have said many times we are working very hard to get one or two players in. I don't know what you call desperate. They [any signings Arsenal make before the transfer window closes] need to make sense and be of quality."
Arsenal boss Arsene Wenger, speaking to BBC Match of the Day: "We lacked experience at the back and we were physically short. Liverpool did well and we were for 15 minutes completely shocked. We pushed players today like Aaron Ramsey. It is an impossible situation to get players back from the Euros and prepare."
Interesting breakdown in the match stats from Opta. As you can see, Arsenal have marginally more of the possession, yet Liverpool had far more efforts at goal - 16 to the home side's nine. An indication of how well Jurgen Klopp's team counter-attacked in the second half, perhaps.
Arsene Wenger has just given a rather terse response to Sky Sports reporter Geoff Shreeves, who asked the Arsenal manager if he felt under pressure after opening the season with a defeat. "I am always under pressure," said Wenger.
More from Klopp: "Nothing is sure until the final whistle. Over the whole of the 90 minutes it was a deserved win.
"We can always score goals and we can defend much better. It's the Premier League and nothing should be easy in this league. Nothing is easy."
"I played a big part in the excitement of the last half-hour, because it’s not allowed to celebrate the fourth goal like this with 35 minutes to go," Liverpool manager Jurgen Klopp says. "At this moment, we switched off the machines. The game was not over. Arsenal lost, but we gave them a path back into the game."
Mowbray concludes by asking Klopp if he plans to get an elastic band for his glasses, to stop them flying off when he celebrates.
The Liverpool manager proves he is a good sport in responding to the question. "If somebody wants to watch me lose my glasses, they can," he says. "I will try to improve on this."
Match of the Day's Guy Mowbray begins his interview with Liverpool manager Jurgen Klopp by asking: "Is that how you expected it to go?"
Klopp laughs loudly. "Exactly," he replies.
More from Arsenal goalkeeper Petr Cech, who looks understandably miffed after being beaten four times: "When you are 4-1 down in the opening game it's sometimes hard to find guts to react but we scored two goals. At 4-1 it is difficult to come back.
"You don't want to lose games. As a player we understand the supporters came with the ambition to win the first game of the season. You have to take the result on the chin. We played well for 60 minutes. We were not good enough for 30 minutes."
A view from a Liverpool fan...
Amir Jiwa-Walji: If we don't sign a new left back, we won't get top 4 this year!
And an Arsenal fan..
David Richard Payn: Remember those that used to scoff at the Wenger Out brigade? Fewer scoffers now, I reckon #bbcfootball
Arsenal goalkeeper Petr Cech, speaking to Sky Sports: "We had a great start to the game. We were organised and controlled the game. It was disappointing to miss the penalty but the reaction of the team was great because we broke through.
"In the second half, the momentum changed because of the free-kick. Liverpool came out with more ambition and were very aggressive. We were punished by the Lallana goal and once we fell behind we opened the game too quickly and allowed them three, four, five counter-attacks."
Now we've got a little bit of time to reflect, let's take a look at arguably the goal of the game - Philippe Coutinho's second, which put Liverpool 3-1 up.
The boffins at Opta tell us that there were no fewer than 19 passes in the build-up.
Liverpool playmaker Philippe Coutinho - who scored twice - has spoken to Sky Sports: "It was a good, tough game. We are happy because we won. The first 20 minutes, we didn’t play very well like the manager wanted.
"We played a difficult game and played really well. We’ll focus on the next game, and take it step by step."
More from Lallana: "Maybe we showed them too much respect in the first half. We came out of the traps flying in the second half and got the second, third and fourth. It was a bit of a tense last 10 minutes on the bench.
"We’ve got huge belief. We’ve got top players on the bench. We’ve got a great squad. We’re not in Europe so we’ll have a lot of weeks where we only have to play one game."
Some quick post-match reaction - Liverpool midfielder Adam Lallana has been speaking to Sky Sports: "It was a very entertaining game.We didn't start so brightly after a good pre-season but it's always difficult coming to Arsenal.
"The manager had a few words for us at half-tim and we responded brilliantly. We got a bit complacent at 4-1, but Arsenal are a top team. We want to achieve something special this year we have to be more disciplined as a unit."
BBC Radio 5 live at the Emirates Stadium
Arsene Wenger has some big, big decisions to make. Does he bring in two more quality players? It was a cracking game. Arsenal didn't give up but I feel they are short in key areas. Liverpool could be outsiders for the title. It's a case of whether they can sustain it.
Liverpool manager Jurgen Klopp strides on to the pitch to embrace his players; the fans who have made the journey from Merseyside to north London are full of cheer. I imagine their nerves are a little shredded too. Not quite as exciting as the last time Liverpool won 4-3, but then that night against Borussia Dortmund in the Europa League in April was truly special.
And that is it. The stand-out match of the Premier League's opening weekend. Superb entertainment.
Santi Cazorla creates space for a cross, and Alexis Sanchez is darting towards the near post... but the ball hits Nacho Monreal on the back and drifts out for a goal kick.
Now or never for Arsenal...
Then it's Liverpool on the break, and a chance for Jordan Henderson to seal the win - but his shot is deflected wide by Hector Bellerin. A corner will do for the visitors, who take the chance to eat up a few more seconds.
Nearly. Theo Walcott has a chance to turn into space inside the penalty area, but trips over the ball. It has been a very mixed afternoon for the England international.
Arsenal have a little more time. Five minutes have been added.
One minute left. Arsenal need a goal against Liverpool. Somewhere in the back of my head, I hear the late Brian Moore's voice: "Arsenal come streaming forward in surely what will be their last attack..."
Final change for Liverpool. Georginio Wijnaldum, who has been lively on his debut, is replaced by Kevin Stewart. I think Liverpool will try to run down the clock from here.
Liverpool's attacking play has been significantly more cautious over the last few minutes, but Georginio Wijnaldum suddenly takes matters into his own hands, picking up speed and feeding Roberto Firmino for a rising 20-yard shot that brushes the outside of the netting after a deflection. Jurgen Klopp's team might need another goal to be certain of victory yet.
BBC Radio 5 live at the Emirates
A big few minutes coming up for Arsenal and Arsene Wenger. We feared the worst for Arsenal at 4-1. The fans were singing 'you don't know what you're doing' and the atmosphere was quite poisonous.
Last 10 minutes. Arsenal pressing patiently. Liverpool centre-back Ragnar Klavan has to be alert to stop Hector Bellerin's cross reaching an Arsenal player in the middle. It's a corner - which Simon Mignolet punches clear. It's going to be a tense finish...
Excellent fact. Technically, the score of this match should be 5-2 to Southampton.
BBC Radio 5 live at the Emirates Stadium
Arsenal haven't given up. Those fans that left early...I think they will be back in the ground.
Answers on a postcard. Or via social media.
Good grief. It might end 4-4 after all. Liverpool's woes at defending set-pieces have returned, although it should be said that Santi Cazorla swung in a lovely free-kick from the left. Calum Chambers got the merest glance with the forehead, and the ball drifted in at the far post beyond the diving Simon Mignolet.
BBC Radio 5 live at the Emirates
You could sense before the game that Arsenal fans were nervous and expecting this. Even when their team went 1-0 up the atmosphere was not rocking. They are looking for Arsene Wenger to go out and spend big.