Arsenal cruised to a 3-0 win over Chelsea on Saturday, scoring all three goals in the first half to claim their first Premier League victory over their London rivals in 10 attempts.

Arsenal gave their manager Arsene Wenger something to celebrate as he marked 20 years in charge of the club, punishing Chelsea for poor defending to race into a 2-0 lead within 15 minutes.

First, Alexis Sanchez pounced on a feeble attempt at a back pass by Chelsea defender Gary Cahill to beat the advancing Thibaut Courtois with a neat chip in the 11th minute.

Three minutes later, Arsenal were 2-0 up as Hector Bellerin found himself in space on the right and picked out Theo Walcott who blasted home from close range.

Chelsea’s attempts to claw their way back were effectively finished in the 40th minute when Mesut Ozil picked up a loose ball deep in the Arsenal half and raced forward to exchange passes with Sanchez and volley the hosts into a 3-0 lead.

The emphatic win was Arsenal’s first over Chelsea in the league since October 2011 and left Wenger applauding a performance of “style and steel” from his team.

He felt Arsenal’s first-half performance was “nearly perfect” but was not about to make much fuss about their special anniversary gift to him.

“Ideally, you want the perfect game and you never get it. We got nearly the perfect first half and that is not bad. Football doesn’t care for history and the anniversaries, just the result on the day. Today we had a good performance,” said Wenger.

His delight was in sharp contrast to the furrowed brow of Chelsea boss Antonio Conte, who oversaw his heaviest league defeat for six years since he was manager of Italian side Siena.

“I think that we didn’t have the right attitude from the first minute,” he said.

“After today we are thinking we must work a lot because we are a great team only on paper.”

He refused to single out an out-of-form Gary Cahill, whose dawdling led to Sanchez stealing the ball off him and opening the scoring.

“I don’t want to talk about the mistake. It is not right for the player. We win and lose as a team,” said Conte.