Wembley Stadium's two giant scoreboards showed 52 minutes when Manchester United's Michael Carrick lost the ball to Manchester City's Yaya Toure after a poor clearance from Edwin van der Sar.
The slender midfielder did not have the strength to win it back from the FA Cup semi-final's most imposing player. The Ivorian held off Carrick and Nemanja Vidic before threading the ball through the legs of the oncoming Van der Sar.
Toure's goal was cathartic, as important as any moment in the recent history of City. The Blues have spent more money than any other club in world football in the past three seasons in a sustained attempt to establish them one of the giants of football.
Big names players with lofty reputations like Carlos Tevez, Yaya Toure, Mario Balotelli and David Silva have arrived in east Manchester at great expense. Cerebral Italian manager Roberto Mancini came in with a mission to make the team regulars among the European elite.
City improved, but not at the pace most expected. They reached the semi-final of the Carling Cup last season - but were beaten over two legs by their loathed enemy from four miles west.
City's league position improved, but they failed to qualify for the Champions League. Thanks to two dramatic derby defeats by United. City fans, one of whom wrote a book entitled Manchester United Ruined My Life were right to curse their red neighbours.
Despite outspending United, City's inferiority complex never lifted. So defence-minded at home in November's Manchester derby that Sir Alex Ferguson goaded them, "If they want to win trophies then you have to attack."
City played well in February's Old Trafford derby, but were defeated again after Wayne Rooney's overhead goal. No matter what the Blues did, they couldn't overcome United.
Privately, City's loyal fans dreaded another defeat on Wembley's grand stage. One gentle soul even reasoned, "Come on, it's our turn now" to Reds on Wembley Way, the main approach to England's stunning 90,000-seater national stadium. Others were less charitable in a mood which was both upbeat and tense on the 200-mile coach trip from Manchester.
The motorways were packed with equal numbers of supporters' coaches carrying fans south to London and moments of humour were frequent. One group of Reds held out directions to any rival fans. United have been frequent visitors to England's rebuilt national stadium, while it was a first visit for City in 12 years.
Tensions mounted as fans goaded each other under the watchful eye of police, United fans chanting: "35 Years" to remind their neighbours that they haven't won a trophy since 1976.
"35 years and we're still here," replied the Blues to emphasise their loyalty to their cause.
City fans replied: "You only live around the corner" - a dig at United's huge support outside Manchester.
That the majority of flags on show by the 32,000 United fans displayed areas of Manchester was of little consequence to the Blues waving inflatable bananas.
Could they beat United when it mattered? Just once. They could and the sustained celebrations after the final whistle showed how much it meant.
A flag in the United end read: "United & City. Joined by Geography. Separated by Success."
It was so true before this game, so very true. United's trophy haul still dwarfs City's, but the Blues are edging closer to that elusive first trophy in 35 years.
And to get their by beating United makes it all the more special for their fans.
FA Cup semi-final report card
Manchester City
• Keeper Joe Hart showed why he is England's undisputed No 1 by making fine saves to deny Dimitar Berbatov and Nani in either half. A
• Defence City never looked comfortable in the full-back positions, but Vincent Kompany was superb and his partner, Joleon Lescott, put in several excellent blocks. B+
• Midfield Lacklustre in the first half, City dominated in the second and Yaya Toure was the heartbeat. He capped his performance by driving into the box to score the winner. B+
• Strikers Like United, City missed their star striker, Carlos Tevez. Mario Balotelli's work rate was way below the standard set by his injured captain. C
• Manager Caught many by surprise by starting with Balotelli ahead of Edin Dzeko. He cleverly pushed David Silva more central. B
Overall Grade: B+
Manchester United
• Keeper Edwin van der Sar's kicking let him down and contributed to the goal. Otherwise he had just one save to make until the final moments. B-
• Defence In almost total control in the first half, but suddenly looked shaky after the break. John O'Shea, in particular, will be disappointed with his second-half display. B-
• Midfield Same story; poor second half. Michael Carrick gave away the goal with a moment of madness, and Paul Scholes saw red to make the comeback even harder. C
• Strikers Dimitar Berbatov missed two chances, within a minute, that would have changed the game. Wayne Rooney would probably have netted one of them. C
• Manager Picked a formation to match City when perhaps he should have been more adventurous. B-
Overall Grade: B-
