Santi Cazorla, Alexis Sanchez and Mesut Ozil's efforts in the opening 45 minutes ensured there was no way back for the hosts
Alexis Sanchez had a hand in all three goals as Arsenal picked up their first Premier League win of the season with a 3-1 victory away to Watford.
Santi Cazorla scored a penalty after just nine minutes following Nordin Amrabat's clumsy foul on Sanchez, and the Chilean doubled his side's lead five minutes before the break with a scuffed finish at the far post.