Arsenal had been hot favourites before the match started, and they immediately showed why.
A fifth minute corner from Henrik Mkhitaryan found an utterly unmarked Danny Welbeck, who hardly had to jump to direct the ball past Daniels in goal.
26 September 2018
The first half was a drab affair, with Arsenal totally dominating in every aspect of the field. However, they rarely looked threatening, content to make the Championship side chase them.
The only moment of real real quality in the first period came in the 38th minute, when Welbeck finished a fantastic team move to make it two for him and Arsenal.
Mkhitaryan, Iwobi and Monreal linked up beautifully, before the Spanish left-back put the ball on a plate for Welbeck to tap into an empty net.
26 September 2018
There were no changes of personnel at half-time, and at first it looked as though there would be no change in the story of the match.
Daniels had to rush out to deny Mkhitaryan from close range, before Iwobi and Emile Smith-Rowe missed good chances to put the game beyond all doubt.
However, in the 57th minute, Guendouzi committed a rash foul on the edge of the box, giving Brentford a brilliant chance to get back in the game.
It was a chance that Alan Judge took with aplomb, curling a brilliant effort into the top corner.
26 September 2018
This did spur on a brief flurry of pressure from the Bees, and Sergi Canos fired over when he might have done better.
However, Arsenal regained control of tha game swiftly.
This was exemplified when Alexandre Lacazette fired home a good finish in injury time, killing the game for good.
Arsenal will march on to the next round, while Brentford will have to focus on the Championship.