There's only really the one question left unanswered - how many will it be?

This Arsenal win was probably sealed the moment Danny Welbeck's second finish left his boot. 

Almost an hour of football later, Southampton are just going through the motions.

Dusan Tadic smells a consolation, he looks for a give-and-go to work space in the Arsenal box, but Ainsley Maitland-Niles is ever vigilant. 

He's still snuffing out the early signs of Southampton danger, with under 10 minutes to go now. 

Image source, Reuters

If Arsenal want more, they need only take it as Sam McQueen hands the ball to Hector Bellerin with a sloppy pass. 

Alex Oxlade-Chamberlain dinks another inventive ball over the top, but Alexis Sanchez can't bring it under. He roars his frustration into the sky. Not a man to take a mis-control lightly.

Ken in Newcastle: You're right Gman (18:43), it was totally even in our 3 zip defeat to Oxford today too. The stats don't lie! 

Scoring goals is definitely overrated. 

Dusan Tadic took the Southampton captain's armband when Shane Long came off but this is poor, a slouching wayward pass that dribbles out of play.  

Any brief Saints momentum fizzes out, before Kieran Gibbs is again muscled off it. Pierre-Emile Hojbjerg drives into the box and finds Tadic, but the yellow shirts quickly swarm around him. 

Sam McQueen drives the loose ball comfortably wide of David Ospina's far post. It's just not going to happen for the home side, is it?

Image source, Getty Images

Josh Sims has probably been the brightest thing about Southampton's attack in this second half. The 19-year-old shows a lovely touch to take a tricky ball under his spell and breeze down the Arsenal right flank.  

But Ainsley Maitland-Niles matches his dart into the box and forces the ball out of play. Good recovery.

Jeff Reine-Adelaide's had a really good game. Off the French 19-year-old midfielder goes, replaced by Nigeria forward Alex Iwobi, 20. 

No sign of the Gunners taking their foot off the gas. 

Danny Mills
Ex-England defender on Radio 5 live

Can we go home?

That was so simple, yet again. Sanchez just runs in behind, he has time to take a touch on the byline within about four or five yards of the goal.

He picks out Theo Walcott and he just has to pick his spot. So, so easy.

Image source, Reuters

Phil McNulty
BBC Sport chief football writer at St. Mary's

Danny Welbeck gets 64 minutes before he is taken off - and what an outstanding 64 minutes it has been on his first start since May 2016, scoring twice and creating the third,

Welbeck's return to fitness is a very welcome addition to Arsene Wenger's attacking armoury and he fully deserved the standing ovation he received from Arsenal's fans.

Image source, Reuters

A promising Southampton move, built slowly through one-touch passing and quick movement into space, crumbles into a disappointing Jordy Clasie shot from the edge of the box. 

Just over 20 minutes left, and the smart money would be on Arsenal increasing their lead rather than Saints reducing it. 

Danny Mills
Ex-England defender on Radio 5 live

You have to remember that Claude Puel wouldn't have known that Arsene Wenger would field a weakened team here tonight. Imagine if Arsenal had fielded their strongest side? Southampton would have been battered!

Here's a few changes, for both teams, that could lift affairs. 

Southampton wingers Nathan Redmond and Dusan Tadic are on, with Shane Long and Lloyd Isgrove making way.

There will be no Danny Welbeck hat-trick today. Off the Arsenal striker goes, replaced by Alexis Sanchez no less. 

Image source, Reuters

The longest spell of Southampton possession in the game so far, but the home side are eventually picked off after a slack Pierre-Emile Hojbjerg pass. 

Arsenal break quickly down the other end, and Danny Welbeck looks to outmaneuver Florin Gardos in the box, but the Saints centre-back holds firm. 

It may just be that we were spoiled slightly by that first half, but it feels like the game's slowed a bit now.

Arsene Wenger is on the walkie-talkie line that keeps him connected with his Arsenal bench. Changes on the cards perhaps?

Image source, Getty Images

Danny Mills
Ex-England defender on Radio 5 live

I think Southampton have almost had one team in the Europa League one team in the league. You need consistency, especially in the back four.

In a game like this they could have changed four or five players and given them a chance to play and learn alongside experienced team-mates.

Southampton are looking increasingly lost without James Ward-Prowse and Oriol Romeu in midfield. Josh Sims again shows a bit of bite about him though, robbing Hector Bellerin and sparking a forward move. 

Pierre-Emile Hojbjerg bends in a cross, which is well fielded by Rob Holding, nodding clear for Arsenal.  

But Sims has got real pace, and as Saints come again the 19-year-old wins a corner off Ainsley Maitland-Niles. Unfortunately, Sam McQueen bends it out of play before it can reach the danger zone.

Gman: Apart from Arsenal's goals the stats imply the game is fairly even.

Unfortunately for Southampton, that isn't how football works Gman...

Another really lovely Arsenal move. Danny Welbeck sells his man with a dropped shoulder, Lucas Perez nutmegs another Southampton defender to find him again with a reverse pass, but Welbeck's shot is blocked. It deserved a goal. 

Just moments before, there were vague shouts for a Southampton penalty as an Arsenal hand struck the ball sliding in to block, but it was very much ball to hand.

Image source, PA

Danny Welbeck. Coming back after eight months out with a knee injury, he looks a man transformed, full of ideas, brimming with confidence. 

For a moment it looks like he's going to shoot first-time after turning a trick from about 30 yards out, but he thinks better of it, travels a bit further, before his eventual shot is deflected wide for a corner.

Image source, PA