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Eden Hazard finished off a wonderful counter-attack in the 25th minute

Diego Costa and Eden Hazard scored as Chelsea beat West Ham to extend their lead at the top of the Premier League to 10 points.

It was the Blues' 21st victory of the league season and another big step towards winning the title in Antonio Conte's first season as manager.

The Italian was once again spot on with his tactics - nullifying the predictable aerial threat of the Hammers' 6ft 4in frontman Andy Carroll early in the match.

And then in the 25th minute his attackers cruelly exposed the hosts' defence with a devastating counter-attack.

N'Golo Kante read a pass from Robert Snodgrass deep inside the Chelsea half on the left and played the ball to Hazard. The Belgium winger drove forward, played a one-two with Pedro and then shifted the ball past keeper Darren Randolph before slotting home.

The Blues doubled their lead after the break when Hazard's corner from the left was turned in with his thigh by Costa - the Spain striker's 17th league goal of the season.

The Hammers came close after Costa's strike when Sofiane Feghouli's low drive was brilliantly saved by Thibaut Courtois. Chelsea wing-back Marcos Alonso then appeared to block Manuel Lanzini's half-volley with his arm moments later - but referee Andre Marriner deemed it to be accidental.

West Ham finally pierced the last line of defence in stoppage time. Carroll robbed Cesc Fabregas and fed Andre Ayew, who squared for Lanzini to fire in.

Chelsea quell Carroll threat

No doubt there were West Ham supporters who would have fancied their team's chances of causing an upset on Monday.

They came into the match having lost only one of their past six league games, picking up three wins. And one of the Blues' four defeats came at London Stadium in the EFL Cup earlier this season.

But perhaps what gave those fans greatest belief of a win was the return of Carroll, back after a month out with a groin injury - and the big striker was central to the Hammers' tactics.

In the opening 20 minutes, both Snodgrass and Feghouli provided the ex-Newcastle and Liverpool forward with high lofted balls. Unfortunately for Hammers manager Slaven Bilic, Chelsea had done their homework as their defenders repeatedly prevented Carroll from having an effort on goal.

He became a peripheral figure in the second half as West Ham looked for a new way of breaching the visitors' defence.

They managed to do so through Lanzini in the dying seconds, but there was too little time to find an equaliser.

West Ham 1-2 Chelsea: Slaven Bilic frustrated to give away 'cheap' goals

Unflappable Blues continue march to title

Not even an intruder who made his way towards the Chelsea players after Hazard's goal could nudge the visitors off their stride. He, like West Ham's attack, was quickly contained.

Chelsea's attack then demonstrated why they are top of the table - the opening goal was a delight.

Kante, who as a defensive midfielder made the second-highest number of sprints on the night - 77 - darted back to cut out Snodgrass' ball. It was then over to Hazard and Pedro, with the Belgian having the confidence and composure to take the ball past Randolph before tucking in.

It was not as good as his Match of the Day goal of the month against Arsenal on 4 February, but impressive nonetheless. Costa, who had a quiet game, then added a simple second after the break.

The Blues did lose their concentration on two occasions: once when Courtois made a great save to block Feghouli's low drive, and then in stoppage time when the Belgium keeper was beaten by Lanzini.

But those mistakes have been few and far between this season.

West Ham 1-2 Chelsea: It's a pity not to keep clean sheet - Antonio Conte

Man of the match - Eden Hazard (Chelsea)

West Ham could not cope with the fastest player on the pitch, who hit a top speed of 34.01km/h. More importantly, his guile, interplay with his team-mates and lethal finishing made him the standout player on the night.

Chelsea hit route 66 - the stats

Chelsea have enjoyed 118 Premier League London derby wins, more than any other side (one more than Arsenal).

West Ham have won only two of their past 22 Premier League clashes with Chelsea, losing 16 and drawing four.

Chelsea are the seventh side to accrue 66-plus points from their first 27 games of a Premier League season, having done it themselves twice before (69 in 2005-06 and 68 in 2004-05). All six previous sides have gone on to win the title.

Chelsea scored the opening goal of the game for the 21st time this season in the Premier League, four more times than any other side.

Chelsea are the only side to use all three substitutes in all of their Premier League games this season.

Lanzini has scored in eight of his 12 Premier League London derby appearances.

What's next?

Chelsea have an FA Cup quarter-final against Manchester United coming up on Monday, 13 March (19:45 GMT) and then it is back to league action the following Saturday when they travel to Stoke.

West Ham are away at Bournemouth in the Premier League on Saturday, 11 March (15:00 GMT).