It is supposed to be to Chelsea’s advantage that they have to leave London only three times in what remains of the Premier League campaign. Really? Are we sure about that? Arsene Wenger always thought it was harder for a London club to win the league because there were so many derbies, and this match rather supported his theory. Chelsea still collected three points but, by Jove, it was tough. Their defence was stretched in a way that it was not at Wembley on Sunday and, by the end, Chelsea were happy to hoof the ball forward or run it into corners to take time out of the game. Eden Hazard celebrates putting Chelsea a goal to the good after nodding Ramires' cross past West Ham keeper Adrian . Adrian dives in vain as Hazard's header sails past the Spanish shot stopper and into the back of West Ham's net . Hazard leads the celebrations as Chelsea took another step towards winning the Barclays Premier League title for the fourth time . Time stands still as Hazard hammers his header home at Upton Park to seal the game in Chelsea's favour . The Chelsea players applaud the travelling fans after clinching another victory as they maintained their five-point lead at the top . WEST HAM (4-3-1-2): Adrian 7; Jenkinson 6, Tomkins 6.5, Reid (Collins 7, 6), Cresswell 6.5; Noble 6.5, Nolan 6.5; Downing 7, Kouyate 7 (Nene 87), Valencia 7; Sakho 7. Subs not used: Jarvis, O'Brien, Demel, Jaaskelainen, Song. Manager: Sam Allardyce 6.5 . Booked: Kouyate, Collins, Nolan . CHELSEA (4-3-3): Courtois 7.5; Ivanovic 7, Cahill 7, Terry 7, Azpilicueta 6.5; Zouma 7, Fabregas 7; Ramires 7, Oscar 7 (Willian 74), Hazard 8 (Remy 96); Costa 7 (Drogba 90+3) Subs not used: Cech, Luis, Cuadrado, Loftus-Cheek. Manager: Jose Mourinho 7 . Booked: Terry, Hazard, Fabregas . Goal: Hazard 22 . Referee: Andre Marriner 7 . Attendance: 34,927 . Ratings by Neil Ashton . Eden Hazard finished off a well-worked Chelsea move to score the only goal of the game. Check out more stats from our Match Zone . West Ham have won a single league fixture since Christmas, but it did not look like it here. They had chances, real chances, to wrest the points from the league leaders, and it says much that Chelsea’s prime performers were once again the central defensive core of John Terry, Gary Cahill and Thibaut Courtois in goal. And Eden Hazard, of course. Always Hazard. He scored the goal, never stopped wanting or carrying the ball, and left the field hobbling, as always, due to a standard battering. Not that West Ham were excessively dirty — Chelsea had four bookings to West Ham’s three — more that a player of Hazard’s ability is always going to attract a certain kind of attention. The group hug that Terry, Cahill, Courtois and Branislav Ivanovic shared at the end should have included Hazard; in his own way, he is as hard as any of them. If Chelsea maintain their supremacy, this is one of those games that will be remembered the day the title is won, one of those they-shall-not-pass performances, all bodies flying, desperate lunges and the ball in row Z if needs be. West Ham were left banging their heads against a wall — no wild metaphor in the case of Cheikhou Kouyate, who ran face first into the back of Terry’s skull late in the second half. Both required treatment, but one came off considerably worse. Hazard runs to Ramires after the pair combined for Chelsea's opening strike which gave Jose Mourinho's men a vital victory . Adrian makes an acrobatic save to keep West Ham in the game as Chelsea threaten to extend their advantage . Adrian keeps out another Chelsea attack as he thwarts Diego Costa on a busy night for West Ham's goalkeeper . West Ham have now failed to score in six of their last seven Premier League matches against Chelsea, including the last five in a row. Eden Hazard’s last four Premier League goals have come away from home after a run of 11 consecutive home goals . It is fair to say if they are ever pondering a fresh material to use in the construction of those black boxes in aircraft, Terry’s cranium may have to be considered. Alas, Diafra Sakho. It is hard to remember a striker getting in so many excellent positions for such paltry return. He knows where to be, he just lacks the clinical touch when he gets there and, thwarted by his own failings and the excellence of Courtois, West Ham drew a blank. Yes, Chelsea could have scored more, too. This was not a one-sided game — but we expect Chelsea pressure on the goal. They have world-class finishers and magicians in midfield. The surprise was West Ham going toe-to-toe with them, particularly, in the second half. Right up until the last minute they were still heaping on pressure. Chelsea have matches at Queens Park Rangers and Arsenal, and a home fixture against Crystal Palace, to come, so nobody should underestimate the challenge to their championship ambition contained in a London derby. This was one of the hardest-fought wins of Chelsea’s season — every bit as much of a proving ground as a wet Wednesday in Wigan, or whatever northern outpost is the current venue for popular cliche. Hazard is the Premier League's most fouled player this season and he goes down after some attention from Mark Noble . Hazard writhes around on the Boleyn Ground pitch in agony but continued to play on for the title favourites . Thibaut Courtois parries the ball with his foot as Nolan closes in during a heart-in-mouth moment for Chelsea's rearguard . Courtois was once again called in to action as West Ham appeal in vain for a handball against Gary Cahill (floored) Mourinho’s favourite scoreline is apparently 2-0 away. He regards it as the sign of a controlled, confident, emphatic performance in a close game. They certainly went in search of it here and came very close on three occasions in the second half. In the 56th minute, a beautiful through pass from Hazard set Ramires clear on goal. He cut inside but his delicate side-footed finish struck the inside of the far post and rebounded into the hands of Adrian. Minutes later, West Ham’s goalkeeper was in the right place again after Terry found Hazard whose cross picked out Ramires at the far post. This time there was no good fortune. The save was superb. There were six minutes of injury time due to the Terry-Kouyate collision and Chelsea came close to wrapping it up then. Hazard broke, for the last time, drawing Adrian yet squaring the ball unselfishly to Willian, whose shot was somehow smothered on its way to the net. The single goal was the fairer margin of victory, however. West Ham did not deserve to appear mastered in the scoreline after a simply thrilling second half. Kurt Zouma gets stuck in against Enner Valencia as the centre half continued to play in the holding role in midfield . Zouma continued in midfield after playing the holding role in the Capital One Cup final, and regularly battled with Kevin Nolan . Cheikhou Kouyate unsuccessfully shoots at goal under the ever-watchful eye of Chelsea skipper John Terry . Cahill attempts to tackle Diafra Sakho as Kouyate is poised to pounce on the loose ball . The first wasn’t bad either, West Ham going close in the 17th minute, when a cross from Mark Noble found a dangerous area at the near post where Kevin Nolan caused localised chaos and Kouyate arrived late only to have his shot blocked by the shins of Courtois. Two minutes later, a run by Enner Valencia opened a gap to slide a pass through to Sakho, who missed his kick. More frustration was to come. In the 37th minute, Carl Jenkinson crossed from the right and the ball dropped perfectly to Sakho, directly in front of goal, but planting his header into the ground, landing safely in the hands of Courtois. After 53 minutes, Courtois saved from Sakho again, pushing out a shot one-handed, just the right side of Nolan. He saved from Sakho after 60 minutes, too, and when he finally spilled a Valencia shot 12 minutes later, the outstanding Cahill cleared as Sakho threatened in vain. It was not all wastefulness by West Ham, though. In the 15th minute, a mix-up by Ivanovic saw Valencia about to speed past Terry and go through on goal. The ever-alert Cesc Fabregas probes into West Ham territory with Valencia and Mark Noble close by . West Ham werew forced into an early change as Winston Reid pulled up in the eighth minute with James Collins coming on in his place . Mourinho and Allardyce share a moment prior to kick-off on a crisp night in east London . The Chelsea captain weighed the odds in a split second and hauled him down, rugby style. Did he prevent a goalscoring opportunity? Probably. Did he play the percentage chance of referee Andre Marriner showing him a red card 30 yards out and early in the match, with Cahill covering, if not really in a position to stop? Undoubtedly. Did he get away with it? Yes. Yellow card. It was a cynical move, but the smart one, too. It was seven minutes later that the winner was scored. To be beaten by a header playing Chelsea is no disgrace; when the man on the end of the ball is Hazard, however, a manager has a right to be aggrieved. Sam Allardyce certainly looked it as the Chelsea man completed a headed goal that was as casually taken as a tap-in, with West Ham’s defence appallingly lax. James Collins had replaced the injured Winston Reid after five minutes, but that was no excuse. The back four had plenty of time to bed in but went to sleep doing so. It was a neat build-up involving Hazard and Cesc Fabregas, who slipped the ball to Ramires overlapping on the right. He had too much room and cut the ball back to leave West Ham flat-footed, Hazard sneaking between the statues to glance a stooping header past Adrian. It was too easy, and it is hard enough to beat Chelsea already — a point Allardyce seemed to be making on the touchline.
Hazard nodded Ramires' cross past Adrian in the 22nd minute to give the Premier League leaders the upper hand . Jose Mourinho's men extended their unbeaten run to seven games . Chelsea maintain their five point lead over Manchester City with 11 games remaining . Check out all the stats from our Match Zone .