But Arsenal just had too much quality. Mustafi had put them in front, before Victor Camarasa levelled following more defensive incompetence from Arsenal in first half stoppage time. Pierre-Emerick Aubameyang had Arsenal back in front just after the hour, before Danny Ward looked to have saved Cardiff a point. Then up popped Alexandre Lacazette, starting a game with Aubameyang for the first time and his winner was exceptional. A thing of beauty.

It meant a rare away win for Arsenal and a second of the season. But with top four the aim, you have to wonder if they will be sturdy enough to get enough over the course of the campaign.

The first half was the ultra high-definition, volume-up showcase of what is wrong with this Arsenal team.

Inside the first seven minutes, Cech was looking desperately vulnerable with the ball at his feet. And not just once – three times, twice in the opening 55 seconds. In the first instance, he made a heavy-footed attempt to sidestep Bobby Reid in order to roll left to Nacho Monreal and came within an inch or two of losing possession a couple of yards from his goal. Emery clapped the attempt.

A moment later, Cech was trying to play square across his goalline to Hector Bellerin and nearly gave Danny Ward a tap-in. It is the kind of manoeuvre you generally learn to avoid sometime before turning 10.

Victor Camarasa slammed his powerful finish past Petr Cech to bring Cardiff on terms on the stroke of half time 

Victor Camarasa slammed his powerful finish past Petr Cech to bring Cardiff on terms on the stroke of half time

The new signing made a heart gesture to the home supporters after endearing himself to them with the equaliser

The new signing made a heart gesture to the home supporters after endearing himself to them with the equaliser

The newly-promoted side were physical and aggressive and caused Arsenal problems in the both halves of the game

The hairiest error of the bunch came on seven minutes, when Cech took a pass-back from Sokratis, and attempted to play through the middle to Granit Xhaka. The ball went straight to Harry Arter on the edge of the Arsenal area and with a better finish Cardiff would have led.

It really takes something to make Cardiff look like an attacking threat and Arsenal on that score were flying. The head-banging mystery is why Cech has been given such an unsuitable brief when they have a £20million keeper on the bench in Bernd Leno, whose work with his feet is known to be good. Cech is rightly regarded as one of the greatest goalkeepers to play in Britain, but retraining this old dog to use a trick with which he is plainly uncomfortable seems bizarre.

But this is Arsenal – it would be no fun if their managers stuck to what everyone else felt was obvious.

In any case, they led on 12 minutes. Granit Xhaka sent over a corner and Shkodran Mustafi beat Sol Bamba to the header for the goal.

Ordinarily, given Cardiff’s struggles in the matter of creating chances, that might have been enough. But not here. Not by a long shot. Danny Ward lunged at a Reid cross and failed to connect when left unmarked and Junior Hoilett launched over after collecting the loose ball. Mustafi was guilty of poor positioning in the build up and again in conceding a chance to Reid a moment later – red flags were going up all over this defence.

Camarasa took a fortunate touch that allowed him room to unleash a wicked strike on goal and send the fans wild