In football nostalgia has always been the file that smooths rough edges off the good old days. You listen to the stories now, poke into the history of the Manchester clubs, and it is easy sometimes to think they were not always football's equivalent of the Hatfields and McCoys or Capulets and Montagues …
The night, for example, City clinched the 1968 title and the victorious team headed for the Cromford Club alongside the United players they had just condemned to second place. Or the evening – a lost evening presumably – when City's assistant manager, Malcolm Allison, threw a housewarming party and the list of those waking up on the couches and the tiles included several of Sir Matt Busby's players.
Brian Kidd remembers that on spare weekends United's players would go to watch City, and vice versa. At 61, Kidd still refers to "the Reds" and "the Blues" and, when raconteurs of this generation start to reminisce, it is easy to think everything was once so much more innocent. "You'd show your player pass and stand at the back of the stand," Kidd says. "It was great to watch. Wonderful times."
Yet there are plenty of other stories to remind us that the two old clubs have been out for vengeance long before Roy Keane embedded his studs into Alfie Haaland's kneecap. Today they will lock antlers at Wembley for the first time. The last time they met in an FA Cup semi-final was 1926, in Sheffield. City won 3-0 but, even then, old scores were being settled, new arguments made. The sepia-tinted pages of the Athletic News tell the story of a City player, Sam Cowan, being "knocked flat down and out!" In the following weeks United's captain, Frank Barson, was investigated and found guilty of what was known in Manchester circles as the "Barson Barge". He was banned for two months.
The rivalry is, in essence, of people who live shoulder by shoulder, shop and eat at the same places and cherish a city where, to quote the late Tony Wilson, "we do things differently" – but who find it difficult sometimes to share the same oxygen. It is not the vendetta that exists between Mancunians and Liverpudlians, which can sometimes feel Sicilian in its intensity. Yet it is still, at best, a deep and entrenched animosity.
Paddy Crerand remembers his first derby, in 1963, as the day he knocked out David Wagstaff in the tunnel at Maine Road. Wagstaff had sworn at him, received a right hook and, in the words of his assailant, "went down like a ton of bricks", in keeping with the reputation that once prompted Denis Law to remark: "If Pat starts, the best thing to do is turn out the lights and lie on the floor."
Yet Crerand, a Glaswegian, remembers it was Nobby Stiles, brought up in Collyhurst, whose derby-day passions burned with the greatest intensity. "We played at Maine Road one year and Nobby wasn't happy that we'd got only a draw so he went mad in the dressing room and started punching the wall."
Mike Doyle, in the blue corner, filled the same role for City and never tired of telling the world about "my hatred for Manchester United". It led to death threats before one derby. His tyres were slashed and rocks were thrown through his windows. Undeterred, he had a chapter in his autobiography titled "Stand Up if you Hate Man U". Doyle is adamant he would have been "set for a spell in Strangeways" had he not been held back from George Best as he sought retribution for the tackle that broke Glyn Pardoe's leg in 1970.
There are not so many Mancunians involved now. For City, there will not be be any local lads at Wembley; for United, maybe Ryan Giggs, Paul Scholes and possibly Wes Brown. It has taken away some of the potential for conflict but it still feels like more than a routine derby. It has become an occasion, just like El Clásico in Spain and El Superclásico in Argentina. No other derby in England gets so much hype, so much attention, so many headlines. A few droplets of Middle East oil riches has made sure of that.
City, under the ownership of the Abu Dhabi United Group, are not merely striving to reach an FA Cup final at United's expense this weekend; they are embarking on a full-scale operation to shift the balance of power. When it will be, nobody can quite be certain. Whether it will happen, likewise. But what we can say with certainty is that they are deadly serious about it.
Sir Alex Ferguson has derided City as a "small club". He has called them "cocky" and "noisy neighbours". Even in his 70th year United's manager will still roll up his sleeves for a scrap when he feels it necessary. He has turned the notorious "hairdryer" on members of City staff and he has taken offence with the local paper – the "Manchester Evening Blues" – for devoting too many column inches to the old enemy. Even now, two years after it became the most talked about piece of Manchester artwork outside The Lowry, little red puffs of smoke start to billow from Ferguson's ears whenever anyone mentions the now infamous Carlos Tevez "Welcome to Manchester" poster.
"He's obsessed with us," says Kevin Cummins, the celebrated Manchester photographer and City fan. "Within the club someone really should have stopped him talking about the Tevez poster because it's all he talked about for months. All he did was make it obvious it had got under his skin – and that he's absolutely terrified of us getting one over on him."
Cummins, the man who brought the music world the photographic history of bands such as Joy Division and The Smiths, went to his first game in 1961 and like many City supporters feels both blessed and cursed. It has been a long wait since the last trophy, the 1976 League Cup, and those barren years have left them open to the schadenfreude of their neighbours.
On the 25th anniversary United's supporters arranged a party in Manchester city centre culminating in hundreds of beery fans marching to Maine Road. On the 35th they used Twitter to dupe unsuspecting celebrities into sending congratulatory "happy anniversary" messages. Ben Stiller, Lord Sugar and Will Carling were among those to fall for it … along with two City youth-team players.
The rivalry threatened to go cold for a few years. Or, at least, it felt very different from what we have now. But that is only because, literally and metaphorically, the clubs were in different leagues.
In Mark Hodkinson's Blue Moon, the diary of City's 1998-99 season in the old Third Division and still probably the best book written about the club, he describes how United were almost a taboo subject behind the scenes. "Sensibly, staff at Maine Road seldom mention Manchester's other team these days. Their hearts might skip a bit when they recall 'the 5-1' – as it has become known – but they know it is old news. United are success, money, glamour and a 1-1 draw with Juventus in the semi-final of the Champions League, while City are failure, debt, calamity and a 2-1 home defeat to Mansfield Town in the Auto Windscreens Shield."
The "5-1" refers to the thrashing of United at Maine Road in September 1989, a defeat that left Ferguson talking about putting his head in the oven. City's victories over United in the following years were small ones: refusing to let employees have red company cars, serving blue ketchup in their hospitality suites.
Frank Clark, one of the 14 different managers (excluding caretakers) they have hired during Ferguson's 24-year tenure, has described it as "the job from hell". He found a club where the local council ran the canteen ("chips with everything") and there was not enough training kit to go round. Niall Quinn, from a few years earlier, tells a similar story about almost having to beg for a pair of boots and being given a pair of socks with a hole in the toe. "City were a hole-in-the-sock kind of club," he once said.
The modern-City are a very different beast even if there are times, such as the 3-0 defeat at Liverpool on Monday, when they lapse into bad old ways. Eastlands, increasingly, has a big-time feel. City can outspend United these days but they also want to outthink them. It is a slick operation: menus put together by Marco Pierre White and John Benson-Smith, electronically heated seats, chauffeur-driven cars. The club have even hired a fleet of drivers, in eight-seat buggies, to offer supporters lifts to and from their cars.
"United have a whole host of problems whereas we are a club on the ascendancy," Cummins says. "This could be the weekend when the order changes and they know it. It's a much bigger game for United in that respect. City have nothing to lose, United have everything to lose. This could be the game that leads 20,000 people to march to Old Trafford to burn down their banner."
Ah, yes, that banner, "the ticker". It has been there 11 years now, permanently jabbing a provocative finger into City's ribs. It began as "24 Years" but the numbers are transferable and it is now "35 Years".
"Over the last few seasons the emphasis on the banner has grown every year," Andrew Kilduff, of Stretford End Flags, says. "Each time there's a cup run a City player now mentions the banner and their motivation to get it down."
Kilduff believes it has become "an obsession" for City. "For the 34th Anniversary, we invited [City's manager] Roberto Mancini to turn the banner round given that he'd said he wanted to get his hands on it. Yet that invite never received the RSVP."
A group of undercover City supporters, colours and loyalties hidden, tried to abduct it on one of the official tours of Old Trafford last year, only to be caught in the act. But will United take it down if City win the FA Cup? Not necessarily so, Kilduff says. "One thought is that it gets turned forward to when City last won the league and becomes 43 years. Keeping it up will just annoy them even more."