* Home wins for Barcelona, Milan, Chelsea
* Arsenal end Marseille run with stoppage-time win
* APOEL continue fine start (Adds detail)
After Manchester took top billing in the Champions league on Tuesday it was London's turn on Wednesday when Chelsea and Arsenal recorded impressive, though contrasting, victories as the Premier League again flexed its muscles.
Chelsea hammered Racing Genk 5-0 at Stamford Bridge to stay top of Group E while Arsenal moved top of Group F after Aaron Ramsey's stoppage-time goal earned a 1-0 victory at Olympique Marseille.
There were also the expected wins for Barcelona and AC Milan, who, at the halfway point of the group stage, both already look sure to progress from Group H.
Less predictable was APOEL Nicosia's 1-1 draw at last year's Europa League winners Porto, which kept the Cypriot outsiders top of Group G.
Manchester United and Manchester City each recorded their first wins of the campaign on Tuesday and still have work to do to make sure of progress but Chelsea can start planning for the last 16 after equalling their record Champions League win against an outclassed Genk.
Fernando Torres, gradually rediscovering his sharpness after a difficult eight months in west London, got two goals while Raul Meireles, Branislav Ivanovic and substitute Salomon Kalou were also on target.
The game was effectively over after Meireles fired home from 25 metres and Torres tucked in from close range inside the first 11 minutes. With Genk missing key players through injury and on a poor run of domestic form, Chelsea went on to record their biggest home win in the competition and equal their best overall - a 5-0 success at Galatasaray in 1999.
"Everybody wants to play. He has been out for a long period but is keeping his form well," Chelsea boss Andre Villas-Boas said of Torres, currently suspended domestically after a red card against Swansea City.
Chelsea have seven points, one ahead of Bayer Leverkusen after the Germans came from behind to beat third-placed Valencia.
Valencia led at the interval through Jonas but Andre Schuerrle smashed in the equaliser in the 52nd minute and Sidney Sam scored the winner four minutes later as Leverkusen secured their first win over a Spanish side in the last eight attempts.
Having won their first two games without conceding, Marseille seemed content to play for a goalless draw once their early efforts came to nothing, and they paid a heavy price.
Arsenal, who like the home side have been struggling domestically, continued to look for the winner and got it in injury time when substitute Ramsey was left alone in the box.
"We made a little step forward but we have to be humble because we are a team that has to continue to grow," said Arsenal manager Arsene Wenger. "The next game at home against Marseille will be very important."
The win took Arsenal top on seven points, one ahead of Marseille. Olympiakos are third on three points after they beat Borussia Dortmund 3-1 in Athens.
An early goal for Andres Iniesta and a late one for David Villa were enough to give Barcelona the points against Viktoria Plzen in a painfully one-sided Nou Camp contest.
The tournament debutants did not manage a shot on goal all night, while the holders managed 18, including two against the woodwork by Lionel Messi.
It was the same score but a very different story at the San Siro, where Milan were grateful for Kevin-Prince Boateng's clincher 20 minutes from time after Belarussian long shots BATE Borisov missed several chances to cancel out Zlatan Ibrahimovic's opener.
Barcelona and Milan both have seven points to the one each of their opponents.
APOEL Nicosia's impressive run continued as they drew 1-1 at Porto to remain top of Group G on five points.
Hulk put Porto ahead after 13 minutes but fellow Brazilian Ailton levelled six minutes later. Porto had plenty of the ball after that but lacked spark and APOEL will be delighted with the point.
Porto have four points, as do Russian league leaders Zenit St Petersburg after they twice came from behind to draw at Shakhtar Donetsk.
At the halfway point of the group stage only Real Madrid, who hammered Olympique Lyon 4-0 on Tuesday, have a maximum nine points.
The action resumes on Nov. 1/2 with the reverse fixtures of this week's games.