Chelsea will spend Saturday evening back on top of the league table following a morale-boosting derby demolition of West Ham.
Alex gave the home team the lead in the first half, only for the visitors to equalise before the break but unlike against Manchester City in the last league fixture, it was Carlo Ancelotti's men who kept their nerve to add three more goals.
Didier Drogba weighed in with two to give him 27 for the season and between those came a goal from Florent Malouda who played as well as anyone as Gianfranco Zola's side were sent even deeper into trouble.
Chelsea (4-3-2-1): Turnbull, Ivanovic (Zhirkov 79), Alex, Terry (c), Ferreira; Ballack, Mikel, Lampard; Anelka (J Cole 65), Malouda (Kalou 86); Drogba.
Scorers Alex 15, Drogba 55, 89, Malouda 76.
West Ham (4-3-3): Green; Spector, Gabbidon, Upson (c), Deprela; Kovac, Parker, Behrami; Ilan (Diamanti 83), Mido (Cole 66), Dyer (Stanislas 66).
Scorer Parker 29.
Booked Mido 49.