To Neil Lennon, an Old Firm game can still prompt vivid recollections of what it is to play in this fixture, to be at the heart of what is often nothing more than a fierce confrontation. He used to revel in the intensity and the antagonism, and Lennon's team has already taken on some of his defiant traits. But there is a sense that we will know more about his players, and his qualities as a manager, when this latest encounter has spent itself.
Lennon has managed Celtic in an Old Firm game before, when they defeated Rangers at Parkhead last May, but the Ibrox side were champions then and it was a victory that carried only a vague significance. Today's meeting is full of intrigue: both sides have 100 per cent records; this is Lennon's first full season in charge, and Walter Smith's last; Celtic will likely field seven debutants, Rangers none; and the three points at stake seem small in comparison to the psychological lift of winning the first of these collisions.
It is only two years since Lennon retired from playing, so he is able to reach for memories that seem fresh with vigour. There was his first Old Firm game at Ibrox, when Celtic won 3-0 in 2001 and Henrik Larsson scored his 50th goal of the campaign, and a 1-0 win in 2004, when Chris Sutton scored to complete a whitewash for Celtic over their rivals that season.
These old times are occasions when Lennon was in the midst of a side that was imposing itself on Rangers, and he understands that to succeed as a manager in Glasgow he will have to achieve that superiority again. Smith, during his two spells in charge at Ibrox, has dominated Old Firm fixtures, but then it is challenges like these – blunt and unremitting – that rouse Lennon.
"It counts for nothing now [last season's 2-1 win], it's in the past, in the history books, and we just look now for the same level of performance. You can't predict Old Firm games, it's very rare that a game of football breaks out in them, it's usually a physical battle and scrappy at times. You're hoping that people go away talking about it for a while after."
Lennon can be an aggressive, almost hostile figure on the touchline during games, prowling and leaping and yelling. His face seems to crease easily into contortion, but then his emotions have always risen close to the surface. He insists that he is controlled during games – even if anger seems readily to hand – but his team has been coldly efficient this season, winning all eight games and conceding only four goals.
Even so, the visit of a Rangers side resilient and hard-edged, but also capable of moments of swift, attacking ingenuity through Vladimir Weiss, Kenny Miller and Steven Naismith, is the sternest of tests. Rangers, too, have won all eight games, and conceded only seven goals, so that the game today seems like a clash of wills.
"[A win] would be huge in terms of how the players feel, it gives you a lift for two or three weeks afterwards," Lennon says. "The onus is on us, we're at home, we're unbeaten, and we want to keep that run going. You don't know [how the players will react]. It's in the lap of the gods. You just hope that their mentality is good. This Rangers team has a good mentality, they don't know when they're beaten. We've shown signs of that as well."
Smith says that he will not send his team out at Celtic Park in the 5-4-1 formation that has served them so well in the Champions' League this season, but the likelihood is that Rangers will look to be strong, resolute and quick to strike out on counter-attacks. It is a style that has served Smith well over the years in games in the East End of Glasgow.
By instinct, this Rangers side is uncompromising, the squad having played together mostly unchanged for thee seasons now. The spirit is adamant, but then Celtic have developed a determination of their own, so that the game seems defined by a grim perseverance. "The squad has got a good togetherness, but to give Celtic credit they seem to have engendered a good spirit in a very short period of time," Smith says. "You will see two teams confident in their own ability to win the match."
For Lennon, it will be a trial, too, of his own composure, of how he can think and act in the conflict of emotions. But he is sure enough of himself to be untroubled. "Other people hype the game up," he says, "we've just got to keep a lid on it."
Celtic v Rangers is on Sky Sports 4 today, kick-off midday