Barry changed into the primary participant to make 633 Premier League appearances, beating a prior absolute best set by way of Ryan Giggs.
But Lacazette’s 20th-minute opener made him the primary Arsenal participant ever to attain in his first 3 Premier League house video games – and the primary since Brian Marwood in 1988 to take action within the league.
The £52.7m signing from Lyon then grabbed a 2nd from the penalty spot within the 67th minute, and in reality he can have had a hat-trick.
But his 4 league targets this season are as many as the entire West Brom group have controlled, and his double used to be sufficient to sentence Tony Pulis to a 10th league defeat in a row right here.
It additionally preserved Arsenal’s 100 in keeping with cent house document this season and earned him a status ovation when he got here off with 8 mins to move.
The two aspects tore into each and every different from the off with possibilities at each leads to a frantic opening.
First, Alexis Sanchez whipped a unfastened kick simply broad with Ben Foster overwhelmed within the West Brom purpose.
Then Barry picked out Jay Rodriguez, who used to be introduced down within the field by way of Shkodran Mustafi however were given up just for Petr Cech to tip his shot off the some distance put up.
Baggies boss Pulis used to be screaming furiously for a penalty however referee Bobby Madley allowed play to move on when he almost certainly will have to have blown.
Pulis used to be even much less pleased with what took place subsequent. His facet gave away some other unfastened kick in a perilous place when Jonny Evans dived in on Mo Elneny.
But this time Sanchez, beginning his 100th Premier League recreation, used to be inch absolute best with the kick, forcing Foster, backpedalling, to tip the ball away off the crossbar.
Unfortunately for him Lacazette used to be there to mop up and he pounced like a real poacher to go house.
Arsenal had received six in a row at house to West Brom within the best flight sooner than this, conceding simply as soon as within the procedure, so the guests abruptly had all of it to do.
Sanchez curled some other unfastened kick broad, and he may even have had a penalty after a blouse-pull Grzegorz Krychowiak which went unseen by way of the referee.
But West Brom have been so on the subject of an equaliser when Krychowiak swung in a pass and Rodriguez beat Cech with a header just for Nacho Monreal to transparent off the road.
Rodriguez regarded as unhealthy as somebody every now and then, and used to be inches clear of connecting with a very good low pass by way of Allan Nyom sooner than the part used to be over.
But the omens didn’t search for West Brom. On the former 47 events they’d led at part time right here within the Premier League, Arsenal had by no means misplaced.
Lacazette, chasing down his strike competitors within the race for the Golden Boot, virtually bagged a 2nd in a while after the spoil.
Sead Kolasinac powered down the left and swung in a pass which Elneny, swivelling, performed proper into the chance zone.
Lacazette used to be on it in a flash and his shot used to be goalbound till former Gunner Kieran Gibbs introduced himself at it to deflect the ball over the crossbar.
If the Frenchman had left it, Aaron Ramsey would have had a good higher likelihood to attain as he used to be utterly unmarked on the some distance put up.
Pulis rolled the cube by way of throwing on Salomon Rondon and James Morrison however issues went from dangerous to worse for his facet within the 66th minute.
Ramsey grew to become Nyom on a run to the byline and when the Baggies defender driven him to the bottom, Madley pointed to the spot.
Lacazette stepped as much as take it, and regardless that Foster guessed the suitable method his penalty used to be proper into the ground nook, and there used to be no long ago for West Brom after that.
Arsenal (three-four-three): Cech; Koscielny, Mustafi, Monreal; Bellerín, Xhaka, Elneny, Kolasinac; Ramsey (Maitland-Niles 90), Lacazette (Giroud 83), Sanchez (Ozil 83). Subs: Ospina, Mertesacker, Wilshere, Walcott.
West Brom (three-Five-2): Foster; Dawson, Hegazi, Evans; Nyom (Phillips 74) Livermore (Morrison 63), Krychowiak, Barry, Gibbs; Rodriguez, Robson-Kanu (Rondon 64). Subs: Yacob, Brunt, Myhill, McClean.
Referee: Bobby Madley