Arsenal strode into the New Year with their lead at the top of the English Premier League intact after a comfortable 2-0 victory over London rivals West Ham United on Tuesday.
Early goals from strikers Eduardo 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 an nervy 1-0 defeat of Birmingham City at Old Trafford.
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 thanks to a late headed winner from Martin Laursen.
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 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.
Arsenal have now won all six of their London derbies this season. "We did the job early and controlled the game," Arsenal manager Arsene Wenger told BBC Radio.
TEVEZ WINNER
United were far from their best against Birmingham and for long periods of the second half were hanging on for the points.
The one piece of real quality came after 25 minutes when Tevez was played in by a superb Cristiano Ronaldo flick and he finished coolly.
The Argentine also hit the woodwork in the second half before limping off with an ankle injury while Birmingham's late pressure nearly brought an equaliser for Mikael Forsell who shot wastefully wide.
Chelsea overcame the absence of a host of big names to win the west-London derby against a Fulham side who were under new manager Roy Hodgson for the first time.
Danny Murphy gave second-from-bottom Fulham a 10th-minute lead from the penalty spot after Moritz Volz was tripped by Joe Cole but they fell away after the break as so often this season.
Chelsea equalised in the 54th minute when Alex nodded a deep corner back across goal for Kalou to head in from close range.
Chelsea took the lead eight minutes later when Clint Dempsey held back Ballack as he sought to reach a free kick and the German dispatched the resulting penalty.
"In the first half it wasn't so good but we came back as Chelsea should," Ballack told Sky Sports.
