The France striker - who has scored in each of those home wins - headed into an open net in the 20th minute after West Brom goalkeeper Ben Foster tipped Alexis Sanchez's free-kick onto the crossbar.

West Brom felt they should have been awarded a penalty before the opener when Shkodran Mustafi brought down Jay Rodriguez with a sliding challenge - but no foul was given by referee Bobby Madley.

Mustafi seemed to clearly catch Rodriguez but referee Bobby Madley chose not to give a penaltyWest Brom boss Tony Pulis cut an exasperated figure on the touchline as his poor record at the Emirates continued.

Pulis was furious when a penalty was not given for Mustafi's tackle on Rodriguez and also disagreed with the decision to a give a free-kick in the build-up to Lacazette's first goal, when the contact from Jonny Evans on Mohamed Elneny looked minimal.

Lacazette's performance was a clear positive for manager Arsene Wenger, who also gave a start to Sanchez for only the second time this season, following the Chile international's collapsed move to Manchester City in the summer.