Chelsea won a record seventh consecutive London derby as they overcame Premier League newcomers Brentford.
The Blues took the lead thanks to Ben Chilwell's strike on the stroke of halftime.
The hosts rallied until the very end, but Edouard Mendy made a series of world class saves to keep the clean sheet.
The Blues opted for a slight change of personnel in this game. Malang Sarr made his Premier League debut, and was joined by Trevoh Chalobah and Andreas Christensen in the back three.
Ruben Loftus-Cheek made a second consecutive league start after his impressive performance against Southampton, and Romelu Lukaku and Timo Werner led the attack for Chelsea.
The visitors opened brightly, with Loftus-Cheek making a signature driving run through the Brentford defence, but the chance fizzled out.
Chelsea enjoyed the majority of the possession in the opening minutes and attempted some nice link-up play going forward.
They looked to press their opponents, with Brentford keen to break on the counter.
The Blues defenders also continued their theme of moving forward out of the backline with the ball at their feet, showing good signs of progression up the pitch.
Lukaku had the first real chance of the game on the 17th minute of play, but his free kick went wide of the post.
Mateo Kovacic was the first player to go into the book after fouling Bryan Mbeumo on a Bees break.
The latter hit the post and Chelsea broke down the far end of the pitch but Lukaku's goal was ruled out for offside; a strong opening 25 minutes from the visitors.
Kovacic was this time on free kick duty, but his effort deflected over the bar and out for a corner which eventually amounted to nothing.
With Chelsea continuing to attack and create chances, Brentford did well to limit their efforts and snuff out danger when required.
Sergi Canos was the first player booked for the hosts for a foul on Loftus-Cheek.
Mbeumo was at the heart of the action again for Brentford, but his cross went straight into the hands of Mendy.
Werner continued to make some great runs on the wings for Chelsea, utilising his pace to drive at the defenders, however his first effort of the game went over the bar.
The German tried to find Lukaku with nearly five minutes left of the first half but Brentford soon cleared.
Premier League debutant Sarr was called into action for the first time in the game and did well to prevent the Bees from advancing their attack.
On the stroke of half time, Chelsea took the lead!
A cross from Azpilicueta aimed for Lukaku was nodded down back into the box, and Chilwell was there to rifle it past the keeper to make it 1-0 and give his side the lead heading into the break.
A deserved lead in the grand scheme of things, but Chelsea still appeared to lack enough quality in the final ball.
The start of the second half saw no changes from either side.
Once again, the Blues began the half well and were quick to attack the Brentford backline but Kovacic's effort was well over the bar.
Sarr did well again to break up an attack from Brentford, this time snuffing out the danger from a long ball.
A Bees free kick after Chalobah's foul on Ivan Toney eventually resulted in a corner for the hosts, but Chelsea soon cleared their lines.
Come the hour mark Brentford were keen to start more attacks and won a couple of corners, but Chelsea's defence remained resilient.
Mason Mount was brought on as the visitors' first change, replacing Kovacic in the midfield.
The goalscorer Chilwell made a good run on the left hand side but Lukaku picked up the loose ball and the linesman raised his flag for offside.
Toney found space just inside the box but opted for a pass to a teammate rather than having an effort on goal.
Lukaku soon had a fantastic chance to double Chelsea's lead but he fired a loose ball over the bar, and the offside flag was raised.
Mendy was called into action for the first time in the 72nd minute as he did really well to turn Toney's volley behind for another corner.
Moments later, he was there once again to clear a long ball down towards the middle of the box.
For the second time, Mbeumo hits the post as Brentford pressed for an equaliser.
Toney was involved in the action once again as he went down in the box under a challenge from Chalobah, but the linesman's flag was raised for offside.
Lukaku was replaced by Kai Havertz with just under 15 minutes remaining.
Captain Azpilicueta was there to block another effort from the hosts before Chilwell cleared his side's lines.
A lofted ball over the top of the Brentford defence nearly found the run of Werner, but goalkeeper David Raya collected it first.
Soon after, there was a scramble in the Blues box. Mendy made a great save to deny Saman Ghoddos and Chalobah cleared a subsequent effort off the line as Chelsea failed to remove the danger.
Mendy, again, was on hand to save his side, this time preventing Pontus Jansson.
Reece James replaced Azpilicueta as the Blues' final change of the evening.
Chelsea's Senegalese goalkeeper made another crucial save in added time, capping a simply superb performance in between the sticks.
The win ensures the Blues return to the top of the Premier League table after Liverpool's win earlier on in the day.
They have now won six games out of eight so far, with only three goals conceded.