Arsenal held their nerve to win 2-1 at Swansea and move clear at the top of the Premier League on a dramatic day which saw both Manchester United and Manchester City beaten.
The Gunners – two points ahead of Tottenham who had earlier drawn 1-1 with Chelsea – recorded a fifth straight league win after second-half goals from German teenager Serge Gnabry (58) and in-form Wales midfielder Aaron Ramsey (62) – netting for a fourth successive game – proved enough to see off the challenge of the home side.
There was, though, a nervy finale at the Liberty Stadium following a well-worked goal from Ben Davies (82), but Arsenal closed out the closing stages to mark Arsene Wenger's 17th anniversary with a hard-fought victory.
Earlier, West Brom heaped more pressure on new Manchester United manager David Moyes with a shock 2-1 win at Old Trafford.
United – thumped 4-1 by rivals Manchester City last weekend – had hit the crossbar through a first-half header from Anderson, but Old Trafford was left in stunned silence when Morgan Amalfitano scored a superb solo effort after 54 minutes.
The on-loan Marseille midfielder collected the ball on the halfway line, surged past both Michael Carrick and Rio Ferdinand before coolly chipping goalkeeper David de Gea as the travelling Baggies fans dreamed of a first away win over Manchester United since 1978.
A curling free-kick from Wayne Rooney which floated through the penalty area and into the far corner soon levelled three minutes later, only for the visitors to again go on the offensive as Jonas Olsson's header hit the crossbar.
De Gea saved a 25-yard free-kick from Amalfitano, before he was beaten again when England Under-21 international Saido Berahino converted the midfielder's through ball in the 67th minute.
Substitute Marouane Fellaini’s conversion from Nani’s cross was correctly ruled out for offside and Boaz Myhill saved from Carrick as United suffered a shock home defeat.
Manchester City also came unstuck as they went down 3-2 at Aston Villa following a second-half rally by Paul Lambert's men.
Yaya Toure slotted home following a corner just before half-time to put City ahead.
Villa – thrashed 4-0 at home by Spurs in the Capital One Cup on Tuesday night – levelled through Karim El Ahmadi on 51 minutes, despite replays suggesting the Morocco midfielder was offside.
City, though, were quick to respond and lead again when Edin Dzeko bundled in a corner five minutes later.
However, Villa were level when Leandro Bacuna clipped in a 20-yard free-kick in the 73rd minute before going ahead seconds later with another quick goal as Andreas Weimann got on the end of a long ball to beat Joe Hart and complete a miserable afternoon for the Manchester clubs.
Cardiff heaped more pressure on Fulham manager Martin Jol as a stoppage-time strike from Jordon Mutch earned the Welshmen a 2-1 win at Craven Cottage.
Hull beat West Ham 1-0 at the KC Stadium, with an early penalty from Robbie Brady – which left Irons boss Sam Allardyce fuming after his side saw two claims for handball were waived away by referee Kevin Friend in the second half.
Southampton maintained their promising start with a 2-0 victory over struggling Crystal Palace at St Mary's Stadium, with a first goal from club-record signing Dani Osvaldo and a 25-yard free-kick from England forward Rickie Lambert sending Mauricio Pochettino's well-organised outfit into the top four.
