Arsenal striker Alexandre Lacazette came off the bench to hand Arsenal all three points from the match but the goal was only given after VAR over-ruled the original offside decision.
The hosts had toiled all afternoon against a resolute visiting Hammers side but made the breakthrough when Mesut Ozil headed Pierre-Emerick Aubameyang’s pass back across goal for Lacazette to smash home.
The referee raised his flag up against Ozil, but VAR replays showed he was just – just onside.
For large parts of the game, the hosts didn’t manage to test ex-Gunners and current Hammers keeper Fabianksi at all as it was the visitors who came closest in a fairly dour opening 45 minutes.
Jarrod Bowen hit the post with a low shot which was dealt away by Bernd Leno who just about got something on to deflect on to the frame of the goal, while Mesut Ozil had our best chance, but his shot in the box was charged down.
There as a real let-off when Michail Antonio and Sebastien Haller broke to isolate David Luiz in the box, but Antonio’s cut-back was just behind his striking partner, who was all alone in front of goal waiting for a tap in.
The 29-year-old Antonio missed from close range late on in the half, but for all our domination of the ball, Arsenal had yet to look particularly dangerous in possession.
Arsenal carved out their first chance of the second half through Bukayo Saka whose moment of invention led Eddie Nketiah to score goal but Fabianski was out quickly to smother the shot.
Antonio again found himself unmarked in the box, but Leno came up with a big save to keep out his header.
The Gunners were struggling and living dangerously at the back, while looking timid in attack after which Mikel Arteta called for Lacazette.
Soon after being introduced, the substitute broke the deadlock to score the seventh goal of the season which was confirmed as a goal by VAR after the referee had ruled it offside against Mesut Ozil the creator of the goal.
Lacazette told the BBC after the game: “I’m happy to score for the team. We worked hard. It was a difficult game. I’m happy. They deserved more because of the chances they created. This is football, sometimes you don’t get what you deserve.
“It is my job to give the manager a big headache. I’m struggling to make the first team but I’m happy to score again today.
“I know that now I have to play well again the next game. Everyone wants to give their best and it’s normal that whenever we do that we will perform as a team.“