It is always a big occasion when the two Manchester clubs go head-to-head, particularly if it is against the backdrop of a recent spending spree that would have made the likes of Real Madrid and Chelsea proud and seen players of the caliber of David Silva and Sergio Agüero land up at the Etihad.

Therefore, when Manchester United and Manchester City met on 23 October, for the first of their two scheduled league games for the 2011/12 campaign, it was not just a regular derby. It promised to be the start of a concerted challenge the blue half of Manchester would offer to the red - a forerunner, possibly, of a change in the power equation.

That was almost exactly what it was.

The Citizens absolutely destroyed the 10 men of United, waltzing past Sir Alex Ferguson's men six times, in a game the grizzled Scot labelled one of the worst of his career.

A brace each from controversial Italian Mario Balotelli and Bosnian Edin Dzeko, with a strike each from Agüero and Silva dwarfed Darren Fletcher's consolation for the hosts, who also had a player sent off.

At the time City were not only five points ahead of the Red Devils (eight, after this thrashing), they had also ended United's run of 19 wins and handed them their first defeat at Old Trafford since April 2010.

It was a clear statement of intent.

Strangely though, the game itself was initially dominated by the Red Devils, with new signing Ashley Young twice testing the visitors' defence. Young was at the forefront of yet another attack after winning a free kick that was somehow scrambled away by Balotelli. To add to the confusion and pressure on City, United's star man Wayne Rooney was controversially fouled in the box by City captain Vincent Kompany, leading to penalty claims that were turned down.

The tone seemed set and despite a summer of awesome spending, it seemed Ferguson's enormous reservoir of experience and inherent steel and class in the Red Devils' rank would be enough to stifle the threat from their neighbours.

However, it was only that City were taking time to settle into their rhythm and once they did... once their passing game established itself, Balotelli struck. The Italian finished sweetly past David De Gea in the United goal, after an assist from James Milner.

That was just the beginning of what was to be a truly horrific afternoon for the Red Devils, who were totally unaware of what was going to happen to them.

The hosts did respond to the opener though, with Anderson and Rooney shooting straight at Joe Hart. Ferguson's men then missed a golden opportunity after defender Jonny Evans fluffed his lines from a Young cross.

The second thunderbolt of the afternoon was the red card - Evans was sent off for his rash challenge on Balotelli. Incidentally, this was at about the hour mark and the score was still 0 -1.

Balotelli dusted off the challenge and compounded United's misery by doubling the score after once again combining with Milner. This was on 60 minutes... the score was 0 - 2.

Nine minutes later, Agüero got in on the act after a run by right-back Micah Richards. United 0 - City 3, after 69 minutes.

The final ten minutes of the game provided for some of the most frantic football Old Trafford had seen in a long, long time.

It all started with Fletcher scoring for United, on 81 minutes; United 1 - City 3.

Then Dzeko, who replaced Balotelli on 70 minutes, joined the party, combining with Gareth Barry to slide the ball past an increasingly helpless De Gea; United 1 - City 4.

An absolutely dominant and ruthless City were not yet done, adding insult to injury and rubbing salt in to their rival's wounds.

Silva scored the fifth, on the counter after a rare United attack; United 1 - City 5.

Dzeko, whose 20 minutes on the field yielded two goals and almost a third, scored his second of the afternoon, after being set up by a rampant Silva.

The final score - Manchester United 1 - Manchester City 6. It was the dawn of a new era.

As we wait breathlessly for the next chapter in this increasingly absorbing rivalry, check out these photographs capturing all the highlights of that now undoubtedly iconic win at Old Trafford...

Manchester United's Manchester City's during their English Premier League soccer match in Manchester.Reuters
Manchester City's Mario Balotelli scores the opening goal against Manchester United during their English Premier League soccer match at Old Trafford in Manchester.Reuters
Manchester City's Sergio Aguero celebrates after team mate Mario Balotelli scored the opening goal against Manchester United during their English Premier League soccer match at Old Trafford in Manchester.Reuters
Manchester United's Nani is challenged by Manchester City's Gael Clichy during their English Premier League soccer match at Old Trafford in Manchester.Reuters
Manchester United's Nani is challenged by Manchester City's David Silva during their English Premier League soccer match at Old Trafford in Manchester.Reuters
Manchester City's Mario Balotelli celebrates after scoring the opening goal against Manchester United during their English Premier League soccer match at Old Trafford in Manchester.Reuters
Manchester United's Nani is challenged by Manchester City's David Silva during their English Premier League soccer match at Old Trafford in Manchester.Reuters
Manchester City's Dzeko scores against Manchester United during their English Premier League soccer match in Manchester.Reuters
Manchester City's Silva scores against Manchester United during their English Premier League soccer match in Manchester.Reuters
Manchester City's Dzeko scores his second goal against Manchester United during their English Premier League soccer match in Manchester.Reuters