Chelsea entered Monday with a chance to go 10 points clear in the Premier League, and it took a step in that direction off a lightning-quick counterattack against West Ham at London's Olympic Stadium.
Eden Hazard finished off the 25th-minute play with a lovely finish on a sequence that started deep in Chelsea's own half.
Summer signing N'Golo Kante started it all by winning the ball and feeding Hazard. The Belgian worked a combination with Diego Costa and finished off the counter by juking goalkeeper Darren Randolph and rolling into a vacated net.
It appeared that a West Ham supporter tried to go after Hazard after entering the field, with stadium security getting to the man before he reached the player.
Diego Costa scored in the second half, and Chelsea fended off a late West Ham rally to take a 2-1 win and go to 66 points through 27 games.
Tottenham is second in the Premier League with 56 points.