Arsenal 2 Manchester United 2: Last-gasp Gallas goes from villain to hero to deny United

Sir Alex Ferguson had said that anyone who had a ticket for this meeting of the Premier League's two leading teams would be "rubbing their hands". As the sides left the Emirates pitch, more than 60,000 observers were banging those hands together in grateful appreciation after a second period that belatedly became something of the game we had been promised and produced a just outcome in a thrilling climax.

Few matches could have borne the weight of expectation with which this one was lumbered, and by half-time it was sagging under the burden. Even then, however, there was the twist of a Manchester United goal just before the interval, to be followed by an equaliser almost immediately after the interval.

From that point, the play flew from end to end, the visitors grabbing the lead with nine minutes remaining before, in added time, an alert referee's assistant spotted that William Gallas's shot had crossed the line before being pawed out by Edwin van der Sar.

The consequences for the title race had he not done so might have been immense. As it was, relieved Arsenal supporters were able to serenade their team with "We are top of the League", understandably not bothering to add "though only on goals scored and after playing seven of our 11 games at home".

In truth, the young pretenders only reached the standards of most previous games this season in limited patches, with Arsène Wenger significantly stressing "character" and "determination".

There were still some admirable individual performances. If Cesc Fabregas often struggled to escape the attentions of Owen Hargreaves, Alexander Hleb maintained his astonishing improvement from the lightweight of his early days at the club, and Mathieu Flamini was again a fine foil to both of them. Gaël Clichy and Bacary Sagna, who made a goal each, were aggressively positive full-backs despite having Cristiano Ronaldo and Ryan Giggs to look after as their principal jobs.

Above all, just, there was Gallas, leading by example at both ends of the pitch in only his fourth match since recovering from injury. "The best way to lead your team is to show character and he did that today," Wenger said. "Our character was tested twice – twice we were down and came back. We didn't find our flowing game and had to rely on our determination and character."

United, facing their most testing examination of the season, were more direct in their counter-attacking than Arsenal, and benefited from a strong midfield defensive pairing of Hargreaves and the vigorous Anderson. Behind them Rio Ferdinand and Nemanja Vidic were solid, helped by Emmanuel Adebayor's tendency to wander out to the flanks. Wayne Rooney was less effective than normal, but when Carlos Tevez faded after a strong first half, Louis Saha came on to help set up the second goal.

Ferguson would have been the more satisfied manager at half-time even if his team had not sneaked ahead beforehand. Pushed back initially, they made the only chances of the first half-hour, with Ronaldo's header from a Giggs corner bouncing up to clip a post and Giggs bundling Ronaldo's cross past a post.

It was not until the 37th minute that Van der Sar was required to make a real save. Gallas ran over to have a word with Fabregas, who was taking a free-kick out wide, then returned to the middle to meet it with a firm downward header that the goalkeeper saved with his legs. With half-time imminent, however, Wes Brown fed Ronaldo, who found Rooney at the near post, stealingin front of Gallas and deflecting the ball in off the defender's hand.

A manager more prone to pan-ic than Wenger might have sent on an extra striker at half-time. Instead, he told Adebayor not to drift out wide, and encouraged the five midfielders to make more runs into the area. Within two minutes, Hleb's determination to keep possession began a move in which Emmanuel Eboué chipped forward for Adebayor, whose volley was blocked by Van der Sar; Sagna was first to reach the rebound, cutting it back for Fabregas, who calmly shot past Ferdinand on the line.

Suddenly the ground was alive again, and so were the home side. Fabregas had a low free-kick saved, Hleb and Tomas Rosicky shot high before being replaced. United still counter-attacked well and Rooney ought to have done better than head Giggs's chip wide. In the 81st minute they regained the lead when Saha played a delicious reverse pass to Patrice Evra, who found Manuel Almunia rushing out at him and rolled the ball square for Ronaldo to tap in.

Even with Theo Walcott and Eduardo on, Arsenal's hopes of a new club record of 25 matches unbeaten seemed to be disappearing. Gallas and the sharp-eyed assistant Darren Cann then ensured another piece of historyfor Wenger after Walcott had miscued Clichy's cross straight to his captain. Ferguson, who will celebrate 21 years at Old Trafford on Tuesday, lamented: "I can't believe it, we've thrown it away."