When people get nostalgic about the Arsene Wenger age, they might persuade themselves that every ordinary afternoon at the Emirates was an ordinary afternoon like this.
Mesut Ozil went off seven minutes from the end and the crowd rose to hail a player who they had expected to salute like this nearly every week while Olivier Giroud scored a wonderful opening goal which also had the benefit of taking away whatever nerves there were.
Ozil was the inspiration for a beautiful Arsenal performance, a performance containing the thrilling interplay which is the hallmark of a Wenger side when things are going well but which has been absent many times when things have been going badly.
Arsenal looked like a side boosted by the victory at Old Trafford but the game was still scoreless approaching half-time as Arsenal, Theo Walcott in particular, wasted several chances.
Giroud, who had been so poor against Monaco, then acted. "There has been no red carpet for him," Wenger said, pointing to Giroud's journey from the lower leagues to the Champions League and insisting that this was a player and a side growing in confidence.
The victories in Manchester this season would encourage the optimistic to believe that something is changing in this Arsenal side, but the pessimistic - and arguably the realistic - would point to the game against Monaco as proof that it isn't.
They have been written off before the second leg on Tuesday but that might be of benefit to an Arsenal side which struggles with the weight of expectation.
The victory yesterday moved Arsenal within a point of Manchester City. It had been an important result in terms of their need to finish in the top four but Wenger was asked if Arsenal were now in the title race.
"We're not in the title race at the moment. We have won eight of the last nine. We are stronger now than we were at the start of the season," Wenger said as he explained that his side suffered after the World Cup. "They understand each other better than six or seven months ago and that makes everybody a lot more dangerous."
West Ham put up more of a fight in the second half but this is not the team that had a bit of verve themselves at the start of the season. Injury has robbed them of key players like Enner Valencia, missing after he cut his toe on a teacup, Andy Carroll and, arguably, Carlton Cole. Their goalkeeper Adrian dislocated his finger in the warm-up but played on and made a series of saves in the first half which made Arsenal more anxious than he should have been.
Even in the second half, while Arsenal had only a one-goal lead, the home side could worry but then Aaron Ramsey scored in the 81st minute and Mathieu Flamini came on to tap in another fine move.
Arsenal should probably have had a penalty in the opening minutes when James Collins - often the last unwavering line for West Ham - clattered into Walcott who would have been better off shooting quickly.
West Ham arrived at the Emirates having won one league game in their last eleven and heading dismally towards the end of the season at which point they are expected to say farewell to Sam Allardyce.
For much of the first half, West Ham played in this desultory fashion, even if they had one scintillating break when Mark Noble, who never stopped hustling, released Matt Jarvis and Kevin Nolan volleyed his cross towards goal but David Ospina parried it away.
Allardyce didn't appear for the post-match press conference because he was, according to assistant Neil McDonald, trying to "pick the players up" but was also "angry".
It was hard to know what he had expected especially once Arsenal took the lead. They had dominated plenty of times and blown it so there was some relief when, in the 45th minute, Giroud combined brilliantly with Ozil and Ramsey before cutting inside Collins and driving the ball into the net.
The goal eased the pressure, perhaps too much, as Arsenal started the second half casually and West Ham could have equalised after Sakho had collided with Ospina and Noble volleyed over Koscielny's weak clearance.
But Arsenal held on. Ozil was influential, although he made a strange choice when he could have shot or picked out Giroud in front of goal but instead tried to land the ball on Ramsey's head at the far side of the box.
That didn't matter when Ramsey played a one-two with Giroud and ensured the three points nine minutes from the end. Flamini then added a third following another bewitching move and everyone seemed optimistic. For Arsenal, that has often been the prelude to disappointment but Wenger insisted his side would go hopefully to Monaco. "If we had no belief then there is no chance,". Yesterday was the kind of day when you'd believe that Arsenal have a chance.
Sunday Indo Sport