David Moyes’ men had briefly looked like spoiling the party at the Emirates Stadium after Marko Arnautovic had cancelled out Nacho Monreal’s second-half opener but two mistakes in the final 10 minutes from West Ham’s defence set the Gunners on course for three points that mean the visitors are still not entirely sure of Premier League survival.
Before kick-off, Wenger was keen to downplay the significance of his third from last game at the ground that stands as an embodiment of his legacy. His focus is still ensuring he bows out with the European trophy that has evaded him these past 22 years.
Wenger had opted to play as much of the side that look set to start Thursday’s Europa League semi-final first leg as possible, leaving Pierre-Emerick Aubameyang - ineligible for continental competition - on the bench and starting Alexandre Lacazette.
Mesut Ozil was, for the fifth time since the start of last season, ruled out with illness and if Atletico Madrid manager Diego Simeone learns anything from today’s game it will be that without the German Arsenal are neutered. West Ham sat deep, Arsenal’s attacks crashing against a five-man defence and midfield quartet, leaving Marko Arnautovic and Joao Mario to spring two-man counters.
For a brief period around the quarter-hour it looked like working. Mario nearly slipped in an overlapping Edimilson Fernandes before Arnautovic got in behind from the left before drawing a parry from David Ospina.
Arsenal lacked any impetus in the final third, Alex Iwobi in particular seemingly unaware that the end of the Wenger era means he will soon have a new manager to impress. If the Nigerian was anonymous Welbeck’s problem was that for all his involvement he couldn’t be relied on to make the right decision.
A low shot curled wide of Joe Hart’s goal, prompting the West Ham stopper to engage in another bout of cynical time-wasting, but too often he went for goal when his best option would have been a pass. Aaron Ramsey was particularly unimpressed when his team-mate shanked a shot wide as he was bursting through a rare gap in the Hammers defence.
Welbeck turned provider early in the second half, chesting a Lacazette cross into the path of Nacho Monreal, whose sweetly-struck volley was too close to Hart.
The Spaniard needed no second invitation as he hammered an Xhaka corner past Hart and into the bottom corner.
By that time West Ham should perhaps have been reduced to 10 men after Pablo Zabaleta hurtled into Welbeck as the Arsenal forward bore down on goal.
With half an hour remaining David Moyes turned to the cavalry, throwing on Manuel Lanzini and Javier Hernandez for Mario and Fernandes. They immediately combined for West Ham’s best opportunity in an hour, the Mexican finding space in the box but heading a free-kick over the bar.
As soon as the Hammers attacked with purpose Arsenal wobbled and the visitors were soon level. Ospina’s diving clearance of a cross did nothing to remove the danger. Kouyate fired in an effort that pinball around the area before Lanzini slipped in Arnautovic, who slammed a precise shot beyond the Gunners goalkeeper.
Wenger threw on reinforcements of his own in Aubameyang but it was Welbeck that went closest, a curling strike 12 minutes from time forcing Hart into a save worthy of a place in Gareth Southgate’s World Cup squad.
Seconds later Hart found himself let down by young defender Declan Rice, who ducked under a Ramsey cross that snuck into the bottom corner.
Hart might have been similarly entitled to complain as Cresswell deflected Lacazette’s shot from a tight angle beyond him.
Further punishment was meted out on a West Ham side who had grown weary in the north London sun, Ramsey drifting through the defence before cutting back for Lacazette to double his tally.