Thrilling Chelsea last minute win over Tottenham
Indeed, the defender cut in from the left past Paul Stalteri and Jermaine Jenas before unleashing an unstoppable drive into the top corner.
Paul Robinson, who had made an amazing save just minutes earlier to deny Didier Drogba, couldn't help it this time.
The game appeared to be heading for a draw, with Michael Essien breaking the deadlock with his first goal for Chelsea before Jenas levelled on the stroke of half-time.
The winner from Gallas means the Blues now need just five more wins from nine games to secure back-to-back titles.
And Tottenham's miserable run against their London rivals continues. They have not beaten Chelsea in the league in 32 attempts, spanning 16 years.
It's fair to say that Chelsea paid tribute to Peter Osgood before the first home game since the sudden death of their legendary striker.
Osgood's family and former team-mates were at the match as the fans paid their tributes with a minute's applause.
The man known as the "King of Stamford Bridge" would have approved when Essien gave the Blues the lead in the 14th minute with a clinical side-footer.
What's more, Michael Carrick had put the Spurs defence under pressure with a sloppy pass to Lee Young-Pyo, which allowed Shaun Wright-Phillips to nip in to steal the ball.
Wright-Phillips, making only his eighth Premiership start of the season, sped into the box and cut a low cross into Essien's path. The Ghanaian midfielder made no mistake, tucking a right-footer inside the far post to put Chelsea ahead.
It's good to notice that Essien should have scored four minutes earlier when he blasted wide with the goal at his mercy. Wright-Phillips dashed onto a long punt from Petr Cech and unleashed a low shot which was parried by Robinson. The rebound made its way to Essien, who had the entire goal to aim for with Robinson out of position, but blazed wide from 12 yards.