The Gunners had started brightly but took the lead through controversial fashion, after Santi Cazorla flung himself to the floor following a challenge by Steven Reid when replays showed there was no contact.
The Baggies, who lost twice last week to halt their fine start to the season, never really recovered from the sense of injustice and there was no way back once Arteta converted from the penalty spot again on 64 minutes after Chris Brunt had tripped Alex Oxlade-Chamberlain.
Source: PA
Source: PA