Goalkeeper Petr Cech endured a miserable English Premier League (EPL) debut for Arsenal as West Ham United ended an eight-year wait for a win over their London rivals with a surprise 2-0 victory at Emirates Stadium here on Sunday.
The goalkeeper signed from champions Chelsea was billed as the player who could make the difference for Arsene Wenger's side as they attempt to be crowned champions for the first time in 12 years this season, but the Czech instead was beaten twice.
Cech was beaten to a Dimitri Payet free-kick by Cheikhou Kouyate who headed home just before half-time and could not stop a long-range Mauro Zarate strike after the break that doubled West Ham's lead.
There was no way back for the home side in their first top-flight match of the season, as West Ham claimed their first victory over Arsenal in 16 attempts stretching back to 2007.
West Ham coach Slaven Bilic celebrated an unexpected three points in his first EPL match in charge.
Arsenal, though, began the match well. Alex Oxlade-Chamberlain, Arsenal's match-winner against Chelsea in the Community Shield last weekend, let fly with a rasping volley that flashed over the crossbar 10 minutes in.
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The winger then surged down the right at full tilt and delivered a cross beyond the far post into the path of Santi Cazorla, but the Spaniard's cushioned volley landed on the roof of the net.
Arsenal were in the ascendancy as Aaron Ramsey's strike from just outside the penalty area looped up and struck the crossbar after deflecting off Aaron Cresswell just after the half-hour.
But It was West Ham who were in front three minutes before half-time, though, as Cech had a moment to forget. He came out to try and punch clear a Payet free-kick from the right, but Kouyate beat him to it and hit the back of an empty Arsenal net with a towering header.
And the home side's task became even greater 12 minutes after the break, when Zarate turned sharply and unleashed a long-range strike that beat Cech at his near post.