It was the kind of tempestuous finale that has come to symbolise these clashes and, out of the madness, Manchester United will cherish their six-point lead over the team that caused them so many hardships last season. But where to start?

The final whistle alone felt like bedlam, with Carlos Tevez and Sir Alex Ferguson contemplating whether to prolong an old argument, Gareth Barry screaming at Roberto Mancini, Rio Ferdinand nursing a line of blood above his left eye and Phil Jones, already booked for inciting the crowd, determined to milk the moment some more.

The Manchester derby is beginning to take the form of those wild, cantankerous United-Arsenal matches of the past. This one will bring a Football Association inquiry, with a coin thrown from the crowd splitting open Ferdinand's brow directly after Robin van Persie's free-kick had reminded the champions of United's brutal habit of scoring late, decisive goals. A few moments later a City fan ran on to the pitch with the apparent aim of getting to the defender. In keeping with the team's performance, that foray did not quite work out as planned.

The drama had plenty of sub-plots – a goal for Ashley Young wrongly disallowed, refereeing controversies, another fit of pique from Mario Balotelli and a supporter arrested on suspicion of racial abuse – but ultimately the most important moment was delivered by the player Mancini identified as his top transfer target last summer only for United to beat him to it. Van Persie had been exquisite and one last swish of his left boot, aided by a deflection off Samir Nasri, meant City's 37-match run without losing a home league fixture was over.

It had lasted the best part of two years but United played with fearlessness. They were the better side, taking a two-goal lead courtesy of Wayne Rooney, and were fully in control until the late pressure that reminded everyone why City's fans like to sing that their team "fight to the end".

The home side dragged themselves level, via goals from Yaya Touré and Pablo Zabaleta, but that told only part of the story and Ferguson would have been enraged, justifiably, if the game had finished 2-2 bearing in mind Young's disallowed goal, ruled out for offside even though he was level with Zabaleta. Yaya Touré made it 2-1 a minute later and United's grievances were exacerbated shortly afterwards when Kolo Touré, on for the injured Vincent Kompany, tripped Patrice Evra inside the penalty area and the referee, Martin Atkinson, waved play on.

That decision threatened to have serious repercussions for United when a corner came out to Zabaleta, with four minutes of normal time remaining, and his shot went through Jones's legs and inside David de Gea's post.

As it was, the visiting team had the greater number of players determined to show they were men for the big occasions. Rooney was an obvious example; Van Persie, too. Yet this was a good day as well for Young, Rafael da Silva and De Gea, among others.

For City, Balotelli was dismal, culminating in the now-customary strop when he was substituted. Nasri was not much better and Mancini did not hold back. Balotelli has all the talent, he said, but is "throwing it out of the window" and the manager's irritation went up another notch when analysing the fact that City had only three players in the wall for Van Persie's goal. In fact, he said, it was "two-and-a-half" – Nasri, turning his back, counts as a half – and he could offer no explanation as to why Tevez had stood in the wall then moved away. He was exasperated, to say the least.

City also had their own grievances with Atkinson, Mancini complaining that he made a number of errors, highlighting a dreadful piece of refereeing when he did not allow advantage after a brilliant Cruyff turn and change of pace had taken Yaya Touré away from three opponents. The bottom line, however, is that City should have been 3-0 down.

Rooney's first arrived on 16 minutes as he scuffed his shot but caught Joe Hart flat-footed after Van Persie's beautifully weighted chest-control had sent Young scampering away. Da Silva, played in by the fit-again Antonio Valencia, created the second on the other side, dispatched this time by a more clinical finish from Rooney's right boot.

After an encouraging start, City's response must have alarmed Mancini – yet the manager had a bad day himself. His team were invigorated once Tevez replaced Balotelli, who should never have started, and the decision to bring on Kolo Touré, rather than Joleon Lescott, was also questionable. Mancini did not want another left-footed centre-half to partner Matija Nastasic, but unfortunately Touré is no longer good enough at this level.

City, to give them their due, considerably improved after the interval. Yaya Touré's goal came in a sustained spell of pressure, firing in after efforts from Tevez and David Silva had been blocked. Before the equaliser, a Silva shot struck De Gea and the crossbar and Sergio Agüero went close twice. United looked like they had blown it. Then Tevez fouled Da Silva and Van Persie stepped forward to deliver the killer blow.

Man of the match Wayne Rooney (Manchester United)