Arsenal moved eight points clear at the Premier League summit after a commanding 2-0 victory at rivals Tottenham on Sunday.
Manchester City fell to a 2-1 defeat at Manchester United on Saturday and Arsenal capitalised to extend their lead with their first away win in the north London derby since 2014.
Hugo Lloris' incomprehensible own goal and Martin Odegaard's sublime first-half strike proved the difference at Tottenham Hotspur Stadium, where a fan seemingly kicked out at Arsenal goalkeeper Aaron Ramsdale at full time.
Antonio Conte's side improved after the interval but a largely uninspiring performance leaves Spurs five points off fourth-placed United, who have played a game fewer.
Lloris handed Arsenal the lead as he inexplicably parried into his own net after Bukayo Saka's tame right-wing cross-shot deflected off Ryan Sessegnon towards goal.
Tottenham's goalkeeper atoned somewhat by keeping out Odegaard's fizzing drive, while Thomas Partey struck the right-hand post with a thunderous volley.
Yet those warnings were not heeded by Spurs, who were 2-0 down when Odegaard was again offered room outside the area. This time, he picked out the bottom-right corner.
Ramsdale denied Harry Kane's header on the stroke of half-time before thwarting the Spurs striker and Sessegnon after the interval with impressive stops in quick succession.
Eddie Nketiah wastefully fired against the onrushing Lloris shortly after, though that mattered for little as Arsenal – despite a late flurry of Spurs pressure – eased to a potentially pivotal victory.
Tempers threatened to boil over at the end, when a Tottenham supporter kicked out at Ramsdale after a confrontation with Richarlison, though Mikel Arteta rushed across to drag his team away from a potential flashpoint.
What does it mean? Gunners end Spurs away hoodoo in vital win
January was labelled by some as defining month for Arsenal's title challenge, with the Gunners having to face Champions League contenders Newcastle United, Tottenham and United.
Arteta's side were far from their best in a goalless draw with Newcastle but improved to dominate this time out.
Victory ended an eight-game Premier League unbeaten run for Spurs at home to Arsenal, who will look to build on their first league double over their rivals since the 2013-14 season as they seek their first top-flight title since 2004.