It is the derby so intense that it dare not speak its name. Celtic v Rangers, you mean?
No, no, no. What we are not talking about - in one of the most bizarre contributions to the build-up to any Old Firm collision - is Ronny Deila's previous exposure to feuds between footballing neighbours.
The man who was plucked from Stromgodset by Celtic to succeed Neil Lennon as manager last summer was asked if anything in his CV could remotely compare with what he will face him when he steps out at Hampden Park for tomorrow's Scottish League Cup semi-final against Rangers.
"At Stromgodset we had a derby with another club," Deila confided, then added: "I can't even say their name. We just called them by their post code - 30/50. It is a place to just drive through."
From then until the end of his pre-match briefing, Deila refused to divulge the identity of his former arch-foes so that, when he eventually departed, there was a rush for Google to settle the issue.
The answer, it transpires, is Stromsgodset v Mjondalen - yes, that old Buskerud County derby. Before he departed, however, Deila did convey some notion of the scale of this Viking vendetta - "That was big for us and it was a full stadium - 5,000 people. It is not the same."
Ronny, it is vastly far from being the same. Multiply the attendance by 10 and the intensity by infinity and one might get some notion of the pent-up anticipation for the resumption of football's most enduring and deep-seated municipal schism.
Yet Deila's Forrest Gump impersonation is not the only surreal element in this drama. The rather more pressing conflicts which broke out in 1914 and 1945 did not disrupt the frequency of Old Firm matches.
Instead, the sequence of square-offs which stretch back to May 28, 1888 - when Celtic won 5-2 in the inaugural derby on their own ground - was ruptured in 2012 when Rangers had to adjust to a new existence in the bottom tier of Scottish football after UK revenue and customs tired of Craig Whyte's disinclination to pay taxes.
In one respect, Rangers have scarcely yielded to Celtic as contenders. The two squads have the highest salary bills in Scotland, but that is as far as the comparison stretches.
Celtic's return for their outlay currently sees them in contention for all three domestic honours and they also have the more exotic prospect of a Europa League encounter with Inter Milan approaching.
Rangers, meanwhile, have all but abandoned even the faintest hope of securing the automatic promotion place in the Scottish Championship at the expense of Hearts.
Celtic play in a half-empty stadium at home because of the absence of plausible rivals; Rangers toil in front of sparse attendances partly because of the fans' estrangement from the Ibrox board - but also as a consequence of some truly dire team performances.
Virtually all logic compels the belief that, if Celtic attend to business efficiently - never mind with fervour - they will emerge with a comfortable victory.
There have been utterances, from players on both sides, of the mantra that "form goes out of the window in this fixture".
In fact, had you placed money on the form team over the past 25 years you would have been rewarded with winnings far more often than not.
Yet, this football match will be contested in a supercharged atmosphere which has no counterpart in the UK - those who have experienced it know that it is driven by unique imperatives.
When Walter Smith was Rangers manager he frequently observed that in Old Firm games he was not motivated by desire to win so much as fear of losing.
"I am one of Walter's students and I now know what he is talking about," said Kenny McDowall, who was unwillingly thrust into the role of Rangers caretaker manager when Ally McCoist was sent on gardening leave last month. "It is an unbelievable game to be involved in. You can watch them as much as you like but there is nothing like actually being involved. Standing in the technical area is unbelievable, just incredible."
Deila might play the country rube at times but he is savvy enough to have no expansive expectations of the occasion. Asked if he would settle for a 1-0 win from an own goal, the Norwegian said: "Of course".
"A week ago you saw Chelsea losing at home to Bradford and Man City losing to Middlesbrough. A cup competition is a special thing and that is why we love it," he added. "This is a semi-final and I don't think the game is going to be great - it will be decided by small margins. Small factors will tip it our way or the other way."
Those factors will include the influence of the most combative individuals on both sides - Celtic's Scott Brown and Charlie Mulgrew and Rangers' Lee McCulloch and Ian Black, to take obvious examples.
Then there are the contrasts, like that between veteran striker Kenny Miller - now in his second spell with Rangers after an interlude at Celtic - and the likes of John Guidetti, on loan at Parkhead from Manchester City. Guidetti's poor recent form, however, could see Leigh Griffiths leading the line.
Or perhaps the issue will be settled by a Dubliner in attack. Celtic have theirs in the shape of Anthony Stokes - but Rangers, for the first time on such an occasion, have a Dub in Jon Daly, the first native of the Republic of Ireland to play in a light blue jersey.
This fixture marks the resumption of an ancient football rivalry, but there is always something new out of the Old Firm. (© Daily Telegraph, London)
Celtic v Rangers, Live,
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