Demarai Gray struck the winning goal as a much-changed Leicester side downed West Ham to pile the pressure on Manuel Pellegrini once again.
With his side languishing 17th in the table, Pellegrini headed into this match under intense pressure but the Hammers boss was boosted by the return of goalkeeper Lukasz Fabianski.
The Chilean made a brave decision to make seven changes to his line-up, including benching captain Mark Noble and Robert Snodgrass, while Leicester boss Brendan Rodgers only retained Kasper Schmeichel and Jonny Evans from their 4-0 defeat against Liverpool.
Whether it was the nerves, pressure or disjointed team Pellegrini had put out, West Ham struggled in the early stages as the visitors controlled possession and Marc Albrighton's effort inside five minutes should've put the Foxes ahead.
There was very little goalmouth action until Kelechi Iheanacho was sent through on goal and Fabianski clattered into the Nigerian striker inside the area. Referee Chris Kavanagh, with no hesitation, pointed to the spot.
Up stepped Demarai Gray but his stance was easy to read and effort a decent height for Fabianski, and the Pole pushed it wide to redeem himself.
Aside from a long-range effort from Arthur Masuaku, the Hammers struggled to create anything that resembled a chance on goal. And then, out of nothing, the home side put together a quick, free-flowing move which saw Felipe Anderson set up Pablo Fornals, who swept home superbly on the stroke of half time.
But it didn't take long for Leicester to get their noses back in front, with Perez again the architect, this time finding Gray in behind the defence and he finished smartly beyond Fabianski.
That goal sapped all belief from the fans about any hope of a comeback and the supporters made their feelings clear with loud boos when Pellegrini brought on Snodgrass for the hapless Carlos Sanchez.
Despite the best efforts of Felipe Anderson and Fornals to create opportunities, the Hammers fell woefully short and the fans began heading for the exits five minutes before the end.
The Hammers failed to conjure up another chance as Leicester cruised to victory to extend the winless run at the London Stadium to six games with the axe looming over Pellegrini.
