Arsenal beat Chelsea 1-0 to go back on top of the Premier League on Sunday, with William Gallas condemning his former club to their first defeat in 17 matches with the only goal of the game.
Gallas scored in injury time at the end of the first half at the Emirates Stadium when he powered in unmarked to head home a corner from the fit-again Cesc Fabregas after Chelsea keeper Petr Cech failed to clear.
The result took Arsenal on to 40 points from 17 games, one ahead of Manchester United, who briefly went top earlier in the day after winning 1-0 at Liverpool.
Arsenal, who played the better football throughout, were denied a second when a Robin van Persie strike was disallowed for offside four minutes from time and Emmanuel Adebayor had one disallowed for a foul shortly afterwards.