Arsenal have opened up a five-point lead at the top of the Premier League thanks to a 2-1 win at Aston Villa.
Craig Gardner put the home side ahead early in the first half.
But the Gunners came back with goals from Mathieu Flamini and Emmanuel Adebayor.
And despite fierce pressure from Villa in the second half, Arsene Wenger's side held on for the win.
Chelsea are up to second after a late strike from Joe Cole settled their clash with West Ham.
The England midfielder latched on to Didier Drogba's pass before rounding Hammers' keeper Robert Green to seal a 1-0 victory.
The Blues have now triumphed in six of their last seven league fixtures.