English Premier League leaders Arsenal displayed typical resilience on Saturday to beat Tottenham Hotspur 2-1 at Highbury to preserve their unbeaten record this season and go four points clear at the top.
Freddie Ljungberg's deflected winner in the 78th minute settled a tight north London derby after Robert Pires had cancelled out Darren Anderton's early strike for Spurs.
But bottom club Leeds United's problems intensified after they crashed to a 6-1 defeat to Portsmouth.
Charlton Athletic moved into fourth position in the League table after a 3-1 home victory over Fulham.
Arsenal have 30 points, four more than Chelsea and five more than champions Manchester United, both of whom have matches on Sunday. Charlton have 21 points.
Arsene Wenger's side left it till late in the game to beat Dynamo Kiev in the European Champions League on Wednesday, and another salvage job was required on Saturday to avert their first defeat at Highbury by Spurs since 1993.
Tottenham fans were dreaming of a first win over their rivals anywhere since 1999 when Anderton anticipated superbly to divert a loose ball into the net after five minutes.
Spurs defended well and Arsenal struggled to create chances until the 68th minute, when French striker Thierry Henry, who appeared to be well offside, but was not shown the flag by the linesman, galloped clear on to a Ray Parlour pass. Though Spurs goalkeeper Kasey Keller superbly saved his shot, Pires was on hand to slam home the rebound.
Ten minutes later Swedish midfielder Ljungberg struck a shot from the edge of the area and the ball looped up wickedly off defender Stephen Carr's boot, over the luckless Keller and into the net.
"They gave a lot on Wednesday night and you could see that, but they had such a strong determination," Wenger told Sky Sports Television later.
The Arsenal manager admitted that Spurs could feel hard done by. "We had a lucky deflection on the winner... We did score a lucky goal, but I think that was the consequence of all our determination."
At Fratton Park the kickoff was delayed for half an hour by a power failure, but it merely delayed the inevitable as Peter Reid's Leeds side lost their seventh game in eight Premier League matches this season.
Leeds, wallowing in crippling debts off the pitch, competed in the first half, but fell apart in the second, conceding four goals.
Gary O'Neil scored twice for Portsmouth, who remain in mid-table after their best win of the season. Leeds stay at the bottom on eight points, the same tally as Blackburn Rovers and Leicester, who did not have a game on Saturday.
Finnish striker Jonatan Johansson scored twice for Charlton as they got the better of London rivals Fulham, for whom midfielder Sean Davis made a scoring return after withdrawing his transfer request this week.
