Chelsea cemented their position at the top of the Premier League with victory over Arsenal as Arsene Wenger's winless streak against Jose Mourinho was extended to 12 games.

The old adversaries squared up in an ugly first-half moment when Wenger shoved Mourinho in the chest in Chelsea's technical area after Gary Cahill's challenge on Arsenal forward Alexis Sanchez.

 A semblance of order was restored although the tension still resurfaced - but as so often, it was Mourinho who had the last word with a win that puts the Blues five points ahead of second-placed Manchester City.

Eden Hazard's first-half penalty put them on their way after he was fouled by Laurent Koscielny, while Diego Costa's ninth goal in seven games since his £32m summer move from Atletico Madrid wrapped up the win.

This never threatened to be a repeat of Chelsea's 6-0 thrashing of Arsenal in March that marred Wenger's 1,000th match in charge of the Gunners, but there was rarely a moment when his side threatened to end his dismal sequence against Mourinho as they suffered their first league loss of the season.