Rumours of a fan protest were well-founded, with many empty seats visible during an otherwise uneventful first hour which yielded few chances before Mesut Ozil curled in a 58th-minute opener.
Theo Walcott doubled the Gunners’ advantage, finishing a slick passing move with a close-range finish 10 minutes later, before Olivier Giroud came off the bench and scored a sublime third to seal his side’s second win in seven games.
Arsenal have 54 points from 29 games, while West Ham, who suffered a fifth straight loss, are 15th with 33 from 31.
* Maya Yoshida and James Ward-Prowse scored within a minute of each other in the closing stages to hand Southampton their first home win since January as they came from behind to beat
Defeat for the visitors ended their run of four successive wins, which included victory at leaders Chelsea on Saturday, and saw Palace stay 16th, just three points above the drop zone.
Christian Benteke opened the scoring in the 31st minute but, shortly after having a penalty appeal turned down,
The result lifted
Middlesbrough imploded after Alvaro Negredo had fired them into an early lead as Lazar Markovic, Baye Oumar Niasse and Abel Hernandez gave Hull a 3-1 advantage, before Marten de Roon pulled one back from an offside position on the stroke of halftime.
The frantic pace dropped after the interval, but Hull held the upper hand and sealed the contest when captain Harry Maguire headed home his first Premier League goal to give the Yorkshire club a fifth win in six home games under manager Marco Silva.