Antonio Conte's dismal London derby form continued as West Ham beat Chelsea 1-0 to hand David Moyes his first victory as Hammers boss.
Moyes' landmark victory was sealed by Marko Arnautovic, who fired his first goal for the club with just six minutes on the clock at the London Stadium.
Alvaro Morata and Eden Hazard spurned chances to rescue a point but the hosts clung on as Conte suffered his ninth league defeat at Chelsea - five of which have now come at the hands of London rivals.
Marko Arnautovic makes it 1-0 to West Ham
West Ham remain in the relegation zone but a first win in nine gives them a timely boost ahead of the busy festive period.
Just as they did in last week's encouraging defeat at Manchester City, West Ham took the lead as Arnautovic played a one-two with Manuel Lanzini and slotted his first Hammers goal beyond Thibaut Courtois on six minutes.