Pep Guardiola had claimed he wanted to see his side “suffer” and then prove themselves at the San Paolo Stadium.

And in a breathless match capped by Sergio Aguero’s ­record-breaking goal, his ­Manchester City side achieved both to reach the Champions League knockout stages in style against relentless Napoli.

In the Italian city under Mount Vesuvius, City’s ­unbeaten start to the season was in danger of going up in smoke when Lorenzo Insigne gave the Serie A leaders the early lead as the home side bossed the game.

But goals from centre-backs Nicolas Otamendi, John Stones, plus Aguero and Raheem ­Sterling – with Napoli scoring from the penalty spot – saw City ­become the first Premier League club to win at the ­intimidating San Paolo.

It was the gritty performance of potential champions. The last team to win here were Real Madrid last March on their way to the Champions League title.

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To face another of Europe’s form sides, Guardiola made four changes from the team which beat West Brom with Aguero, Danilio, ­Sterling and Ilkay Gundogan recalled.

With David Silva and Yaya Toure on the bench, there were no starters from ­Roberto Mancini’s team which lost 2-1 here six years ago.

Former Liverpool keeper Pepe Reina ­appeared in his 161st European game to move fifth on the all-time list. City were two goals up after 13 minutes at the Etihad but this time Napoli dominated the early exchanges – and ­dominated possession. Marek Hamsik sent in the first long-range shot and then Dries Mertens twice tested Ederson.

It needed a superb near-post clearance by Stones to clear the danger after a short corner but Napoli ­pressure told after 21 ­minutes.

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The manager rejoines with the fans at fulltime (
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Getty Images Europe)
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Insigne exchanged passes with Dries Mertens before ­clipping his shot over the ­advancing ­Ederson for his fifth goal since mid-­September.

It took the subbing off of left-back Faouzi Ghoulam by ­Napoli boss Maurizio Sarri (left) – and a shoving match between Aguero and ­Kalidou Koulibaly – to spark City into action. After Gundogan went down under challenge on the edge of the box, the Argentine’s spat with the Napoli defender ­continued long after the ball had been cleared.

City immediately counter-attacked and Aguero’s low shot was narrowly deflected wide.

But, like in the first game, the momentum had shifted.

Gundogan had shot deflected over before his cross following a Kevin De Bruyne short corner was headed in at the far post by Otamendi after 34 minutes. The Argentine defender could have put City in the lead but fluffed another chance ­before Stones headed against the bar.

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Action Images via Reuters)

And Sterling had a claim for a ­penalty rejected after a ­shoulder charge from Elseid Hysaj. City started the second half still on top and a last-ditch tackle from Hysaj was needed to stop a Sterling run.

But from Sane corner after 48 minutes, Stones hit the bar again with a header and this time the ball bounced down and over Reina’s line.

The £47.5million England ­defender also scored two ­headers against ­Feyenoord in the opening group game. But Insigne hit the bar from the edge of the box before Napoli drew level with their third spot-kick against City in two games.

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The manager rejoines with the fans at fulltime (
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Getty Images Europe)

Raul Albiol went down under Leroy Sane’s challenge and Jorginho rolled home.

Ederson then made a superb save from Callejon as Napoli pushed for the winner.

But from a home corner, Sane led a lightning breakaway ­before he was stopped and Aguero put home the loose ball.

And Sterling drilled home a fourth in injury time from a De Bruyne pass.