Robin van Persie's deflected injury time free-kick secured a significant 3-2 victory for Manchester United against Manchester City on Sunday, in a hugely entertaining derby at the Etihad Stadium.
City, the reigning Premier League champions, thought they had secured a dramatic draw thanks to Pablo Zabaleta's 86th minute strike - but Van Persie stepped up in added time to swing in a 25-yard free-kick that clipped Samir Nasri's outstretched leg and nestled in the far corner to clinch all three points.
The home side were woefully out-of-sorts in the opening 45 minutes and deserved to go two goals behind thanks to Wayne Rooney's twin strikes, but Yaya Toure's cool finish on the hour mark - just seconds after Ashley Young had a third United goal incorrectly ruled out for offside - raised hopes of an impressive turnaround.
Zabaleta's late intervention then restored parity, before Van Persie swung the balance of the contest decisively with his dead ball finish, a mixture of great technique and - thanks to Nasri - unpredictable good fortune.
United moved six points clear atop the league table as a result, although there was further controversy at the end after Rio Ferdinand was involved in an altercation with members of the crowd.
Ahead of the game City, perhaps aware of United's recent frailty from set-pieces, opted for last season's Old Trafford derby hero Mario Balotelli up front alongside Sergio Aguero, with the influential David Silva also fit to start. Sir Alex Ferguson, meanwhile, paired Van Persie and Rooney in attack, with Jonny Evans at the heart of defence as the Scot refused to risk Nemanja Vidic.
A few heavy tackles flew in early, before both sides settled into a passing rhythm. The first chance of real note in the game arrived after 10 minutes; Balotelli volleying wildly over from 10 yards after Silva's perceptive pass had given Zabaleta space to fire in a cross from the left.
Six minutes later City had another opening, but Balotelli overhit a pass as Aguero threatened to spring clear. Seconds later United were ahead, however, the away side springing up the other end of the pitch almost immediately as Ashley Young took the ball on from Van Persie's deft flick and played in Rooney, who cut inside beyond Gael Clichy before scuffing a right-footed shot that rolled agonisingly beyond Joe Hart to his right and into the corner.
A second blow followed for City soon after, as captain Vincent Kompany was forced off with a groin injury, to be replaced by Kolo Toure (despite Joleon Lescott also sitting on the bench). The defensive reshuffle initially seemed to unsettle the home side, who needed Joe Hart to race from his line to clear as Young threatened to get through one-on-one.
As opening and entertaining as the game was at either end, it was always United who looked more dangerous - with Rooney grabbing his second of the game just before half-time. This time it was a one-touch finish from the Englishman, who buried Antonio Valencia's low cross from the right after finding space in the box. It was the 27-year-old's 150th Premier League goal.
City, perhaps chastened by a dressing down from manager Mancini, came out the stronger in the second half - winning a corner almost immediately and playing higher up the pitch as United struggled with their own defensive issues, with Chris Smalling thrown on to replace the limping Jonny Evans.
Mancini responded with his own change - Balotelli, who had rarely been anything other than lackadaisical all game, being hauled off after one particularly lax attempted backheel in favour of Carlos Tevez.
The change did not make an immediate impact, although Aguero did soon have De Gea panicking for a second as his curled effort from 25 yards flew just high and wide of the far post. City then romped forward again, with Rio Ferdinand at full stretch to deflect Silva's cross out of the reach of the sliding Aguero.
With less than 60 minutes gone United then thought they were three ahead - with Young incorrectly ruled to be offside as he turned home after Van Persie's exquisite effort had bounded away off the bar. Remarkably, seconds later the deficit was then halved - De Gea making a fine double save from Aguero and Silva before Toure calmly passed home when the ball was played back to him.
By this point the game had really sparked into life - Patrice Evra thought he had won a penalty after going down under Kolo Toure's half-hearted challenge, before the Frenchman scampered back down the other end to prevent Tevez getting a clean shot at goal.
With 12 minutes remaining it looked like City would have their equaliser - but Silva could only watch on in disbelief as his close range shot deflected off De Gea's shoulder, onto the crossbar, and away. Tevez then flashed a difficult chance over, before Edin Dzeko - a super-sub on a regular basis for City this season - entered the fray.
The equaliser, when it came, arrived from a less likely source. A City corner was not properly cleared by the jumpy United defence, and Zabaleta was perfectly placed to rifle home a low drive that De Gea had no chance of stopping.
City then went off in pursuit of a scarcely-believable winner, but they were destined to be hit by an absolute sucker-punch late in the contest. Rafael won a free-kick on the edge of the box after a foul from Tevez, an opportunity that Van Persie - shrugging off team-mates - immediately stepped up to take.
The Dutchman curled the ball at goal - but it was a deflection off Samir Nasri, making a half-hearted attempt to block the strike, that sent it spiralling towards the far post, with Hart once again unable to keep it out as it nestled in the corner.
That decided the match but the drama was not quite over - with investigations almost certain to be launched after Hart had to intervene as Ferdinand - sporting a bloody head wound - was confronted by an onrushing fan after celebrating Van Persie's crucial - and potentially title-deciding - goal.
Everton showed City how it is done as they scored two late goals to snatch victory as they beat Tottenham 2-1.
Spurs looked to be leaving Goodison Park with all three points after Clint Dempsey's second-half strike, but goals from Steven Pienaar and Nikica Jelavic - both in added time - saw the Toffees leapfrog their rivals into fourth place.
David Moyes' side, who were without a win in their previous four matches looked in danger of slipping six points behind Spurs after Dempsey's effort put Tottenham ahead. Just moments after Spurs keeper Hugo Lloris was called into action to deny Leon Osman, Dempsey was given too much space, and his speculative effort from 30 yards deflected off Sylvain Distin and looped over Tim Howard.
Pienaar thought he had rescued a point for Everton against his former club with a perfectly-time run to nod in Seamus Coleman's cross, but it turned out to be all three as Jelavic met another cross from the right - poking the ball past Lloris to secure a dramatic victory.
Three former West Ham players helped sink their old club as Liverpool came from behind to win 3-2 at Upton Park.
Glen Johnson, Joe Cole and Jonjo Shelvey - all products of the Hammers' youth academy - were on target as the Reds secured back-to-back wins to climb into the top half of the table for the first time this season.
Brendan Rodgers' side, who were without top scorer Luis Suarez, went ahead in style as they took the lead after just 11 minutes. Finding himself on the edge of the area, Johnson fired a superb effort beyond Jussi Jaaskelainen from 25 yards.
However, the home side rallied and were rewarded for their determination with a penalty after Guy Demel's powerful volley from the edge of the box struck Joe Allen's raised arm. Mark Noble stepped up, and although Reina dived low to his right, he was unable to get a fingertip on Noble's well-placed effort.
The Hammers went into the break with their noses in front - with the impressive Matt Jarvis delivering a dangerous ball from the left, and Steven Gerrard nodded the ball into his own net after colliding with team-mate Daniel Agger.
Liverpool got themselves back on level terms after a lovely sweeping move; Raheem Sterling slotting the ball through to Cole, who finished with a neat left-footed strike. And a third former Hammer ensured all three points for Liverpool; Shelvey beating James Collins to Jordan Henderson's cross from the right - although the goal was credited as an own goal by Collins.