James Lawton: Sergio Aguero delivers on his promise with golden shot to transform Manchester City

With City behind, Mancini became a figure of torment, pleading and raging

It required a superior footballer – and competitive man – to impose a little order and quality and character on something that was otherwise destined to be remembered as one of football's most expensive and unbridled disasters.

That it finished something quite different from that in the pale spring sunshine of east Manchester, that the most neurotic fans in English football found themselves stumbling joyfully from a Stephen King movie to something more worthy of Walt Disney, and were able to sing at last "We are the Champions", was because such a man announced himself at almost the very last moment.

Sergio Aguero not only saved Manchester City's title in circumstances that had become surreal.

He also made his entry in City's billion-pound title inventory shine with a new brilliance.

At £38m he is, officially at least, City's most expensive signing – one day he may be dislodged from this honour by a full accounting of the Carlos Tevez deal – but shortly before 5pm last night in a part of this great city which until the last few years has not often been associated with extreme wealth, the obligation was to weigh Aguero in the purest gold.

Not only did he win back a title that was ebbing away in a way that would have fulfilled the most sinister fantasy of the Manchester United manager, Sir Alex Ferguson, who had talked so darkly of the psychological damage City might collect with a shocking failure against Queen's Park Rangers, he confirmed something he had promised early this season when he made his first appearance in this stadium.

It was the delivery of a new dimension to English football's most lavishly rewarded but still under-achieving mercenaries. He came on a substitute against Swansea City, linked sublimely with David Silva for one goal, scored two others of bewitching authority and suggested most powerfully that it might certainly be the first night of the rest of City's life.

So it proved here on an afternoon of withering tension, which towards the end seemed to be threatening a particularly heavy toll on the man who was carrying the most pressure.

The City manager, Roberto Mancini, had protested that his job would have survived a pratfall on the last lap. Maybe, maybe not, but when City became enmeshed in the desperate trenches of 10-man QPR's defence, after Mario Balotelli had been sent on in place of Tevez as the running, volatile evidence that here indeed was a crisis of unexpected weight, Mancini became a figure of torment, pleading, entreating, raging.

You could hardly say it was an over-reaction, not when you were reminded of the level of expectation which had been created in this half of the city, nor when you recalled the extent of investment – and least of all in the context of the huge advantage which came to his side when Joey Barton, masquerading for a while as someone you might entrust with a football team in highly pressurised conditions, got himself sent off in the most disgusting manner.

His assaults on Tevez and Aguero were cheap shots which brought a fresh burst of dismay to all those who see in his Twitter volume a searcher after truth rather than a head-banging recidivist. However, his disappearance should have made the City task that much simpler. Instead, it became an intensifying nightmare after goals from Djibril Cissé and Jamie Mackie sent shock waves across English football – with perhaps one or two of them even reaching the Middle East – and injury to the great and influential Yaya Touré.

Mancini was stripped of his favourite option when the going becomes a little problematical, as it did at Newcastle the week before, and the big man from the Ivory Coast was pushed forward to break an impasse and inject new levels of confidence.

Yesterday, the vital moment of breakthrough appeared to have been achieved when Touré was helped off the field to be replaced by Nigel de Jong. Pablo Zabaleta had pushed City ahead and suddenly there was the sense of impending celebration. It was that feeling of well-being that sometimes precedes an ambush.

For City, the wounds could hardly have run deeper right up to the moment Aguero delivered salvation. Edin Dzeko set up the rescue and then Diego Maradona's son-in-law did something that placed him in the folklore of a club now measuring itself for a sustained impact on the English and European games.

He carried his club across the line. He did it in that way that he had promised from the start, the way of a player who is not easily deflected from his task, who believes that his destiny is not just to enjoy the most enviable of lifestyles but also to win. When Aguero fulfilled all of that promise, when he shot City out of their ultimate anti-climactic misery, he may also have lifted the club – and the project – not just to a title but a new way of seeing itself.

Maybe it won't happen overnight. Perhaps there is some serious work to do on the building of some of that culture of winning that gets into the bones. Yesterday, City, it has to be said, were not so heavy with such quality. In fact, they might easily have woken this morning to the kind of devastation that Ferguson was so desperately wishing upon them.

That they didn't suffer such a fate was a finely run thing even by the standards of a season in which the only certainty was that nothing could be taken at face value. It was desperate and at times it seemed to become impossible, but City kept playing, and they kept reminding themselves, the fine captain Vincent Kompany said later, that they had done rather too much to let all of it slide away on a tide of bitterness they would never be able to forget.

The prospect had, of course, been one of coronation but soon enough that possibility had become besieged by doubt. So it meant that City simply had to fight for what they believed had become their right. Aguero's brilliant statement was that they may indeed become a lot stronger at a place where they could have been broken – and shatteringly so.

The title in figures

55

Home points for City. Equals the Premier League record.

1,066

Number of goals this campaign, a record for a 20-team PL season.

18

Clean sheets for Joe Hart in the league this season.

93

League goals by Man City this season, at a rate of 2.4 per game.

89

United's points, a record for a team finishing second.