Van Nistelrooy, who had been violently jostled and taunted by the Arsenal players after he missed a penalty that would have given United victory in the corresponding fixture last season, coolly sent Jens Lehmann the wrong way from the spot to put United ahead 17 minutes from the end.

His strike partner Wayne Rooney, who had won the penalty, then applied the final fatal blow in stoppage time, side-footing home Alan Smith's cross from close range.

It was Arsenal's first defeat in the league since a loss to Leeds in May 2003 effectively handed United the title and it is one that is likely to leave a legacy of lasting bitterness given the nature of the crucial penalty.

Television replays suggested Rooney had gone down extremely easily after the lightest of contacts from Sol Campbell. But referee Mike Riley had no hesitation in pointing to the spot and van Nistelrooy did the rest.

As a spectacle, the match was disfigured from the outset by challenges that spanned a spectrum from the mildly reckless to borderline malevolent and which, for the first 35 minutes, Riley was peculiarly reluctant to sanction.

Ashley Cole was extremely fortunate to escape a booking after clattering into Ryan Giggs inside the first two minutes but he could not escape the lunge from Rooney that followed 60 seconds later.

That set the pattern for a stop-start contest in which neither side was able to play with sustained fluency.

A more open encounter may have ensued had United managed to exploit the eighth minute chance that fell to Ryan Giggs after Kolo Toure charged down Rooney's shot from just inside the area.

The loose ball fell to Scholes who immediately returned it to Rooney. The teenager's cut-back wrong-footed the Arsenal defence but Sol Campbell was able to recover in time to block Giggs' shot from just behind the penalty spot.

Arsenal had another scare shortly afterwards when Lehmann scuffed a clearance straight at Ronaldo, whose first-time pass caught van Nistelrooy only fractionally offside.

It was the visitors however who had the better quality chances and they had considerable cause for complaint when Edu sent Freddie Ljungberg sprinting clear of the United back four mid-way through the opening period.

The Swedish midfielder appeared to be barged over by Rio Ferdinand but referee Mike Riley judged the challenge legitimate.

Another chance went begging when Dennis Bergkamp's control let him down as he received Jose Antonio Reyes's neat dink into the box, allowing Roy Carroll just enough time to close him down and block.

United had further reason to be grateful to Carroll three minutes before the interval when Edu, drifting in from the right, played Thierry Henry in behind his France team-mate Mikael Silvestre.

Again the Northern Ireland goalkeeper was quickly off his line to narrow the angle and block Henry's attempt at a chipped finish.

Arsenal's dominance extended into the opening stages of the second half, which saw Bergkamp squander another gilt-edged opportunity. Ljungberg was the creator, beating Gabriel Heinze on the right touchline before delivering a low cross that Bergkamp pulled wide of the target.

As things were to turn out, that was to prove Arsenal's last chance of extending their winning run to 50 matches in their biggest rivals back yard.

Arsene Wenger's men can console themselves however with the knowledge that they remain eight points clear of United in the Premiership table.

Elsewhere, controversial striker Craig Bellamy brought an eventful week to a remarkable conclusion by claiming an 89th-minute winner for Newcastle in a seven-goal thriller against Manchester City.

England hopeful Shaun Wright-Phillips looked to have snatched a point for the visitors with his 77th-minute strike, but the Welshman claimed the points at the death with a clinical fiinish to make it 4-2.

Kevin Keegan's former club looked to be flying after Laurent Robert's superb 49th-minute free-kick and a 56th-minute Alan Shearer penalty put them two up, but Wright-Phillips sparked an unlikely fightback with a 64th-minute strike and substitute Robbie Fowler levelled from the spot three minutes later, only for Robbie Elliott's header to creep home two minutes later.

Southampton clawed their way off the bottom after a bitty 0-0 draw with Birmingham.

The Saints, still to win under head coach Steve Wigley, did have the better of the first half and Dexter Blackstock's header bounced off the top of the crossbar.

But the visitors, this season's draw specialists having arrived at St Mary's on the back of four successive stalemates, improved after the break.

And only a superb diving stop from keeper Antii Niemi denied a winning volley from David Dunn.

Stewart Downing's late strike cancelled out Diomansy Kamara's fine effort as Middlesbrough and Portsmouth shared the spoils at The Riverside.

The in-form Boro youngster rifled home a shot from 18 yards 16 minutes from time to earn Steve McClaren's side the point their attacking football deserved.

Portsmouth took the lead as early as the fourth minute when Kamara embarked on a mazy run which ended with a low left-footed strike past Mark Schwarzer.

But Harry Redknapp's troops were on the back foot for the rest of the second half and Shaka Hislop produced fine saves to deny Downing and Jimmy Floyd Hasselbaink, while Yakubu cleared a Szilard Nemeth header off the line.

The Boro domination continued after the break, with Hasselbaink, George Boateng and Nemeth all going close before Downing pounced.

Mark Viduka had a glorious chance to grab a winner as time ran out, but Hislop pushed his header onto the underside of the bar before the ball was scrambled away to safety.