Their idea of heaven is a drizzly winter’s Saturday, a gutful of lager and fish and chips, with the family clad in the green and white hoops of their storied Celtic Football Club as they cheer from the terraces of Celtic Park, the cauldron that is their hallowed home pitch. Planted with shamrocks from Ireland, they call this place Paradise, though it’s anything but around here.

In the hardscrabble surrounds is a massive necropolis; the nickname Paradise, then, is a nod not only to the heroic deeds their club’s loyal servants have performed for 120 years, but a sardonic nod to the stadium’s next door neighbour, too.

Both are venues Glasgow’s long-suffering Eastenders know only too well. The club’s exploits here have earned them the Scottish championship 42 times in 122 years, and, now well clear at the top of the table, Celtic seems assured of a 43rd title this season. Only one team has a better record – the hated Rangers from across town.

And on the grim streets around the necropolis, male life expectancy hasn’t much changed from the Victorian era when the cemetery opened for business, a few years before Celtic began playing here. Glaswegian men here, live an average of just 54 years, lower than in war-torn Iraq and Gaza and famine-racked North Korea. People living just a few kilometres away do so for 28 years longer.

It’s a little sobering to consider that many of the burly, middle-aged men who’ve come here today, some of the 53,000 Glaswegians I’ve shouldered alongside to be seated at Paradise, may not be around much longer.

Still, caught in the Celtic moment, mortality doesn’t seem much to matter today. We’re all here to savour one of world sport’s most enthralling occasions – a Celtic home game in a seething stadium British sports fans regard as one of the country’s most atmospheric arenas.

The place is abuzz. The stadium’s loud speaker announces the teams as they run onto the pitch, and as they finesse their skills pre-game, the crowd builds up a voice. We roar through continuous choruses of Britpop anthems before launching into Depeche Mode’s totemic Just Can’t Get Enough. It’s deafening and I’m convinced the chants must be raising the necropolis’ tenants, and audible to the Highlands beyond, too.

But now, a hush. The announcer solemnly intones that the noble Celtic is not so much about sport as it is about society, a community gathered together to overcome. He reads the club’s mission statement from Hoops, the club’s matchday programme.

These are fine words that could’ve been penned by Nelson Mandela himself, with the drafters of the United Nations’ Universal Declaration of Human Rights nodding approvingly.

Celtic, we learn, “is run on a professional basis with no political agenda…the Club has a wider role and the responsibility of being a major Scottish social institution promoting health, well-being and social integration”.

Moreover, Celtic stands “to maximise all opportunities to disassociate the Club from sectarianism and bigotry of any kind … to promote Celtic as a club for all people, regardless of gender, age, religion, race or ability”.

Indeed, underlining the mantra is Celtic’s current playing squad, a masala of Korean, Nigerian and Israeli midfielders, a Honduran defender and a Muslim striker from Sierra Leone. Of the 34 players in Celtic’s top squad, only seven are Scottish, and then just three from Glasgow.

It’s stirring stuff. The stadium’s big screen is showing soft-focus clips of an outreach program the club has mounted in Thailand, sleek footballers, resplendent in club colours, showing their skills to Thai kids with Down Syndrome.

Problem is, the crowd’s attention span has been exhausted, and we’re not exactly linking hands to sing Kumbaya at the earnest inclusiveness of the message.

No, we’re far more arrested by what’s going on at the other end of the stadium, where the notorious toughs of Celtic’s Green Brigade are in full voice, conveying an entirely different message – one at the edges of hate.

Though we’re packed in to see Celtic tackle third-placed Motherwell, they’re really an afterthought. The Green Brigade’s real enemy isn’t Motherwell but a team that’s not even playing, Celtic’s sectarian rival, a mortal foe in more ways than just football, that hails from the other – Protestant and Unionist – end of the Glasgow divide.

That would be Rangers.

It’s been a bad week for the famous club from Ibrox, in Glasgow’s near-as-deprived West. Forged in the shipbuilding foundries of the Clydeside docks, which built the warships that built and defended Empire and Realm, Rangers has just gone into administration, 140 years after the club was founded. (It is 16 years older than Celtic.)

It’s an ugly story that’s dominated Scottish media and the chatter of pubs and kitchen tables here. Every day, there seems to be a newer, more shocking revelation about the depth of the crisis Rangers faces. There are claims of corruption and fraud and fingers pointed at hands in the till as the club totters at the edge of extinction.

Not least of Rangers’ problem is a potential £75 million tax bill, which the club says it can’t pay. Its senior players have taken 75 per cent pay cuts to keep it afloat, as desperate fans dig deep to save their club. An emblem of Queen and country, Rangers’ woes couldn’t come at a worse time for the Unionist cause in Glasgow, as momentum for Scottish independence builds on the republican base that is Celtic’s heartland.

It’s all pretty grim at Ibrox, and don’t the Gaels at Paradise know it? No matter that Celtic is playing the perfectly solvent Motherwell, the Paradise crowd seems keen to pretend that it’s Rangers lining up out there for slaughter.

The Green Brigade leads the stadium into well-practised verses of Bye Bye Rangers, sung to the tune of Bye Bye Blackbird. Then, if anyone was in any doubt where loyalties lie here, they switch to Bye Bye England for a spirited few more.

There’s no sympathy at all for Rangers, nor much for Her Majesty’s United Kingdom either, just gloating schadenfreude that’s gathering ahead of 2014, when Scots vote in an independence referendum.

And then, the day’s pièce de résistance. To an ecstatic roar, the Green Brigade unfurls the banner that the faithful have been waiting for.

Stretching over several sections of Celtic Park, the banner shows the HMS Dignity, painted in Rangers’ unionist colours of red, white and blue, disappearing beneath choppy seas. Rats in team ties – the club’s board – scurry to abandon ship carrying treasure chests of loot and booty, the corruption metaphor. As the Dignity sinks, a seaworthy craft in Celtic’s Gaelic tricolor looses off a missile for good measure, assuredly consigning Rangers to the deep. The catastrophe is captioned “Rats Drown.” And all this just seconds after those worthy words from the announcer urging the stadium to follow “The Celtic Way”.

Maybe they took him at his word. Such is the bitter sectarian rivalry between Dublin-leaning Catholic Celtic and London-inclined Protestant Rangers that neutral Scots have even coined a name for it – the Old Firm.

Their domination of the competition is beyond dispute; since 1904, the Scottish championship has been won just 12 times by teams that weren’t Rangers or Celtic. It’s been 27 years since a club other than the Old Firm won the title. That’s impressive – but it’s what happens off the field that can shame Scotland and expose the country’s deep-seated rifts.

One might say, all this is just the one-eyed passion of football fans the world over.

Yes, and no. Bad things happen when Rangers play Celtic. In 2009, the Glasgow region’s Strathclyde Police found that reports of domestic violence spiked by 41 per cent on days the two met in big matches. Last year, the BBC reported that on the Saturdays during the 2007-2011 football seasons when the Old Firm were drawn apart, instances of violent crime averaged 140 across Strathclyde. But on the Saturdays when the Old Firm was playing each other, that number leapt to 382.

Those figures have since come down, thanks to a police crackdown, but at a price. It costs Scottish authorities nearly 30 times more to police a Celtic-Rangers clash than a match in which these clubs aren’t playing.

Ask the family of Celtic manager Neil Lennon if it’s all just about football. In mid-2011, he and two other high-profile Celtic supporters, as well as the offices of Cairde na hÉireann – the main republican organisation in Scotland – received nail bombs in the post. Two men are currently on trial in Glasgow’s High Court for these crimes; 42-year-old Neil Mackenzie and 43-year-old Trevor Muirhead.

They both deny the charges but the proceedings have the city chattering as eagerly as the Rangers’ ongoing travails. Last week the trial jury was shown an oath of allegiance to the “Scottish Unionist Association”. It said: “I, Trevor Muirhead, am a Protestant by birth and being convinced of a fiendish plot by Republicans to destroy my heritage, swear to defend my comrades and my country by any and all means against Republicans and Republican offshoots that may be of similar intent.”

Talk like this alarms moderate Scots, who congratulate themselves that the independence debate has so far been conducted peacefully. It raises the ominous spectre that Scotland has so far avoided, as the independence issues get thrown around – that it could become Northern Ireland.

That’s a nightmare scenario few Scots dare contemplate, and so far the debate has been spirited and well-fought on all sides.

Which is more than one can say for the epic and ongoing battle that is Glasgow’s Old Firm, that threatens to break out of the seething confines of Paradise.