Only the two Manchester clubs had beaten Fulham on their travels in the Premier League this season prior to kick-off, and Marco Silva’s men opened this contest with all the swagger of one of the division’s best away sides.
Within six minutes Alex Iwobi teed up Harry Wilson to volley against the crossbar, but building on that early momentum was proving difficult against a resolute Hammers rearguard.
The contest shifted on the 27-minute mark - by which point West Ham were yet to have a single shot - when Carlos Soler’s free-kick was headed home by Max Kilman. That strike was ruled out for offside, but the home fans weren’t made to wait much longer for the opener.
Fulham were caught out as they looked to play out from the back, with Andreas Pereira’s blind square pass was pounced on by Soler, who wrongfooted the retreating Bernd Leno to break the deadlock.
Just two minutes later, Potter’s men doubled their advantage as a well-worked counter ended in a cross that reached Aaron Wan-Bissaka at the back post, and the full-back brilliantly squared for Tomas Soucek to convert.
Fulham were stunned, conceding from the only two shots they faced before the break.
Raul Jimenez was the second Cottager to strike the woodwork in the lead-up to half-time, though their deficit was halved soon after the restart when Iwobi’s cross evaded everyone on its way in.
The comeback was briefly on, only for another defensive howler from the visitors to restore West Ham’s two-goal lead.
Just four minutes after coming off the bench, Danny Ings pressured Leno into an error in possession, allowing Lucas Paqueta to finish into an empty net for his fifth goal of the season.
While Silva was enraged at another basic error, his side refused to lie down and reduced the arrears again in almost identical fashion, as Iwobi’s cross was attacked by Wilson.
The Welshman failed to make contact, but the ball again evaded all comers on its way past Lukasz Fabianski.
A stern test awaited for West Ham’s defence, but it was a poor finish from Adama Traore - who blazed wide from close range - that ensured victory would be theirs.
It brings Fulham’s nine-match unbeaten run across all competitions to an end, while the defeat marks their first loss in an away London derby in the league in almost a year to leave them off the European pace and just four points clear of the Hammers.