Tottenham had closed the gap on the pacesetters to four points with a 4-0 defeat of Watford at White Hart Lane, which was also settled in the first half after goals from Dele Alli, Eric Dier and Heung-min Son.
Son tapped in Kieran Trippier's cross 10 minutes into the second half to complete the scoring and bad top spot on the highlights show. There was another big cheer when Harry Kane returned from injury as a substitute just past the hour mark.
An own goal from Adam Smith was quickly followed by a fine solo effort from Eden Hazard to effectively put Chelsea's result beyond doubt inside the opening minutes. Joshua King notched just before the break but Marcos Alonso settled matters with a fine free kick 22 minutes from time.
FULL MOTD RUNNING ORDER (10.30pm - 11.55pm)
West Brom 0 Southampton 1
Liverpool held on to third place with a 2-1 win at Stoke, where they came from behind to get the three points. They also claim third spot as their own in the programme.
Jonathan Walters headed a close-range goal from Xherdan Shaqiri's cross to give Stoke a 44th-minute lead, prompting Reds boss Jurgen Klopp to make changes at half-time.
Philippe Coutinho volleyed a 64th-minute equaliser, before fellow substitute Roberto Firmino gave Stoke goalkeeper Lee Grant no chance with another volley two minutes later.
Liverpool goalkeeper Simon Mignolet had a hand in preserving the three points for the visitors with a good save to deny Saido Berahino soon after.
Manchester City stay fourth, and are in the fourth slot, after a comfortable 3-1 defeat of Hull at the Etihad Stadium.
City took the lead just past the half hour when Jesus Navas' cross was turned into his own net by Ahmed Elmohamady, then Sergio Aguero doubled the lead three minutes into the second half.
Fabian Delph wrapped up the win in the 64th minute with a well-struck 20-yard effort, before Andrea Ranocchia pulled a goal back for the strugglers with five minutes remaining.
At the other end, West Ham eased their fears with a 1-0 win over struggling Swansea, with Cheikhou Kouyate making the decisive breakthrough with a low shot just before half-time.
Southampton reached the 40-point mark as Jordy Clasie's well-struck 25th minute goal gave them victory by the same margin at West Brom.
However, second-bottom Middlesbrough were frustrated by Burnley, with the Clarets' Robbie Brady wasting the game's best chance in the 56th minute of the goalless draw on Teesside.