Simon Kelner: Two football clubs separated by success, but a city united in pride

The BBC made a tactical mistake, I think, in the presentation of its decision to move some of its operations to the North of England.

By insisting on geographical exactitude, it offered 1,500 staff the opportunity to move to Salford, a city rich in industrial heritage and the birthplace of such diverse characters as Albert Finney, Emmeline Pankhurst and John Cooper Clarke, but which, unfortunately, gives its name to the electronic tag worn by criminals: the "Salford Rolex". Why on earth didn't the BBC say it was moving to Manchester? After all, the boundaries between the two cities are pretty indistinct, and go largely unnoticed by locals. For those London types who get a nosebleed when they have to go north of Hampstead, Manchester just sounds a bit better, and if the Beeb had thought about it, they might have had less trouble persuading, say, the number four presenter on Breakfast to forsake her Victorian terrace in Wandsworth and exchange it for a magnificent detached house with a view of the Lancashire moors.

There's a Cath Kidston in Manchester, you know. And Harvey Nicks. And the Hallé Orchestra. And trams. And Michelin-starred chefs. And great libraries, galleries and museums. And ... And ... Oh yes, and two of the current top four football teams in England. That's right: two of the best football teams. For many years, it used to be just the one, but today, at Wembley Stadium, Manchesters United and City play an FA Cup semi-final that has a significance beyond what happens on the pitch. In football terms, it's a clash of aristocratic pedigree and new money – City run on the petrodollars of an Abu Dhabi sheikh – but this is more than a contest between noisy neighbours that takes place 200 miles from home (because a match at Wembley generates more gate receipts). Above all, for those of us who were born in the city, it's a day to celebrate being a Mancunian and to reflect on what it means to be a Mancunian.

First of all, let's dispense with the popular idea, a legend among football folk, that United supporters don't come from Manchester. (Typical joke: How many Man United fans does it take to change a light bulb? Two. One to change the bulb, and the other to drive from Cornwall.) The truth is that more people in Manchester support United than City. But whereas City's following is drawn almost exclusively from the city itself, United have a widespread and multi-national fan base. So what makes you a sky blue or a red? It's not a religious thing, like Celtic and Rangers, or even Liverpool and Everton, although United once had strong Catholic links. It's partly geographical – there are areas that are staunchly for one club or the other – and it's partly success-based; if you were born, for instance, since 1976, the last time City won a trophy, you might consider opting for the club more likely to have open-top bus parades.

It's also a question of demographics: City's supporters tend to come from the poorer areas of Manchester. Its fabulously appointed ground – built for the 2002 Commonwealth games – is in Beswick, a district which, according to its short Wikipedia entry, "has been known for its deprivation and poverty" and is thought to be the inspiration for the Chatsworth estate in the TV series Shameless. (In fact, in one episode of the programme, there's a memorable scene when some of the leading characters sing an especially obscene anti-United song.) According to the most recent Fan Survey undertaken by the Premier League, which ranked clubs' supporters by average salary, City were in 12th position, several places below United, and well under the league's average.

Contrast that to the riches of the club itself, now under the ownership of Sheikh Mansour. He's already lavished £300m on players, the main reason why, after decades of underachievement, City can now go toe-to-toe with United. Rivalry is as fierce now as at any time in history: United supporters unfurl a banner at every home game with a reminder of how long it is since their neighbours last claimed one of the game's prizes. (It changes with the seasons, but it currently reads 35 years.)

Failure, often achieved from the most promising position, has lent a certain romance to supporting City. Its anthem, "Blue Moon", has a pathos of its own, while the resigned humour of its long-suffering fans is well known. Red is the colour of thrusting achievement; sky blue is not, although it has a definite aesthetic appeal. In the film Control, the wonderful biopic of the life of Joy Division singer Ian Curtis, the lead character says he supports City simply because he loves the colour of the shirts. I may be more than a little biased here, but there is a coolness to supporting City that one hopes the vulgar excesses of Arab money won't erode. Noel Gallagher supports City and Mick Hucknall supports United. Say no more.

So, this afternoon, whole swathes of London will echo to the nasal sound of thousands upon thousands of Mancunians. They'll be loud, uncouth and probably unruly (they are football fans, after all) and you'll see them doing the Gallagher swagger. They'll be chippy, all right: most South-of-England-born people I know regard chippiness as the defining characteristic of Mancunians. And there's no gainsaying that we're resentful of the fact that we live in a nation unfairly defined by its capital city. We're not unusual in being sensitive when people treat our heritage with casual disregard. But I believe Mancunians also have an innate self-confidence; after all, we're from a city which has nothing to prove, to itself or to anyone else. Not for us the indulgent mawkishness of Liverpudlians, or the introspective, grudge-against-the-world attitude of some of the other great cities of the North.

As befits somewhere which was once the most important industrial centre in the world, Manchester looks outward, and has a spirit of invention and enterprise, epitomised most recently by the way it responded to what the IRA did to its commercial centre in 1996. The bomb blew a hole, literally, in the city's economic infrastructure, but out of the destruction grew the opportunity to rebuild the whole area around Market Street, the main shopping thoroughfare, and to demolish the original Arndale Centre, one of the ugliest buildings in England.

Today, Manchester feels like a stylish European city, with modish shops, pavement cafés, striking public spaces, and a modern, environmentally sound transport system. When, in 2006, Labour became the first political party to take its annual conference to Manchester, the leader's speech was preceded by a film, to a booming Oasis soundtrack, that showed the very best aspects of the city. There's a tram, there's some smart people enjoying a cappuccino, there's the magnificent Gothic town hall, there's the Royal Exchange Theatre, there's a des res canalside development. It was designed to give the audience a lovely, warm feeling about the achievements of New Labour. And it's true, one of the best things the Blair administration did was to help revive some of the great cities of Britain. As I watched the film, I felt tears well in my eyes. It wasn't that I was moved by the realisation that governments can indeed improve the quality of life of its citizens. And it certainly wasn't that I was feeling sentimental about Tony Blair, whose last conference appearance this was. No, it was something deeply unfashionable, which could only be called civic pride. I felt proud of my city, of its achievements, of its people, and this gave way to a profound sense of belonging. I haven't lived there for many years, but it was at that point that I realised – and I possibly speak for many of those who will descend on London today – that I'm a Mancunian first, and an Englishman second.