Arsenal strode into the New Year with their lead at the top of the Premier League intact after a comfortable 2-0 victory over London rivals West Ham United on Tuesday.
Early goals from strikers Eduardo da Silva and Emmanuel Adebayor did the damage at the Emirates as Arsenal completed the double over a side that beat them home and away last season.
Manchester United, who lost top spot on Saturday after a surprise 2-1 loss at West Ham, kept close on the tail of the Gunners thanks to a Carlos Tevez goal in a 1-0 defeat of Birmingham City in front of an Old Trafford crowd described by manager Alex Ferguson as "funereal".
Arsenal have 50 points from 21 games, two points more than champions United, while Chelsea have 44 after coming from behind to beat Fulham 2-1 in a lunchtime kickoff with goals from Salomon Kalou and Michael Ballack.
Everton moved up to fifth after a 2-0 victory at Middlesbrough while Aston Villa are sixth following a 2-1 home defeat of Tottenham Hotspur.
Portsmouth won 2-0 at Reading where the home side played virtually the entire match with 10 men after Ibrahima Sonko was sent off in the fourth minute.
Fourth-placed Liverpool are not in action until Wednesday when they welcome struggling Wigan Athletic at Anfield.
West Ham have a knack of springing surprise results against title chasing sides and are still the only visiting team to win a Premier League match at the Emirates but on Tuesday they were left with an impossible task.
Arsenal, who have now won all six of their London derbies this season, needed less than two minutes to take the lead when Eduardo pounced with a sharp finish to follow his double in the 4-1 win over Everton on Saturday. The game was effectively over after 18 minutes when Adebayor threaded in a shot from an acute angle.