This was a day of green smoke and red mist, and a game of nerves and then nirvana for Celtic. The final seconds of this Scottish Premiership showdown were unimaginably tense. Celtic had the lead, they had the extra man, and they had the trophy gleaming more in their sights.

But some of their players were running through quicksand, and the last few minutes dragged like hours. Rangers, depleted in numbers but not spirit, kept coming back at them, helped by Philippe Clement’s changes, especially bringing pace out wide.

Rangers threw everything at Celtic. Clement’s assistant, Alex Rae, sprinted to recycle a loose ball, to keep the momentum. Their keeper Jack Butland strode up for a corner. His Celtic counterpart, Joe Hart, withstood the pressure.

In front of Hart, the imperious Irish centre-back, Liam Scales, kept defying Rangers, clearing another Ross McCausland cross. Celtic Park was in ferment, and now torment. Their fans cheered in relief as Anthony Ralston eased the pressure, driving down the right, and then dissolved in sighs as he lost the ball to Ben Davies and back came Rangers again. By now Celtic fans were desperately contesting the legitimacy of a throw-in award for Rangers, anything to carry their drained players over the line.

So when the excellent referee, Willie Collum, blew for a final whistle only the start of it was heard. It was swiftly drowned out by the sound of 60,000 in green and white celebrating. A fan on crutches waved them in the air. Countless others filmed the scenes on the pitch, loving the sight of the vanquished Scott Wright on his haunches and Ross McCausland lying shattered and broken on the greenest of pitches.

READ MORE:  The Brazen Head to Ibrox Museum: Henry Winter's Celtic vs Rangers tour

They snapped away as Hart strode towards the main stand, blowing kisses to his family as a fan threw a scarf towards him. Hart has done so much for Celtic, still a committed professional at 37, and he will be much missed when he retires this summer. Coaching, and family time, await. He bows out a winner, fittingly, given how much he has given in his 20-year career. Six points clear and with two games remaining, Celtic surely will be crowned champions now. As Hart headed out of view, supporters leaned over the tunnel parapet and waved him on his way.

Their day had worked out. For this was a day of two shows, on and off the pitch at Celtic Park. What turned into a momentous day began early. Before 9am, the green tide rolled through town, through the barriers at Queen Street station, young lads, groups of four or five, chattering, excited, knowing what this meant. A woman with a thick green-and-white scarf, neatly folded, almost caressed in her left hand, waited patiently for those she was heading to the game with.

Fathers and sons walked from the station into the sunshine, sharing a memory, a strengthened connection, finding a familiar haunt for breakfast before heading out to Paradise. Closer to the ground, green and white gushed from Dalmarnock station, the streams of humanity becoming a river.

One had a Tommy Burns No 10 scarf from 1982/83. Another was wrapped in a Celtic-Borussia Dortmund half-and-half scarf. The wardrobe were threads of history. One fan wore a T-shirt celebrating Lubo Moravcik as “a gift from God” as fans called him. They haven’t forgotten his elegant contributions to the goalscoring work of Henrik Larsson. Another fan strolled past, shirt off, revealing a large tattoo of a dreadlocked Larsson on the nape of his neck. The man himself was here, needing four stewards to ease him through the adoring throng outside.

When the Rangers bus arrived shortly before, Celtic fans were kept 20 yards back behind the barriers but certainly made their voices hear. “Get your hair cut, Cantwell,” was the most printable.

The Herald: Todd Cantwell' received some comment from Celtic fansTodd Cantwell' received some comment from Celtic fans (Image: PA)

A few offered predictions to anyone would hear. “We will win 2-0,” insisted one. “Because we have the best players, best manager, and the best-looking fans.”

Celtic also had the only fans here. The absence of away fans made for a strange atmosphere, still raucous and intense and loud but self-evidently one-sided, almost like a rally.

“Football without fans is nothing,” read the famous saying of Jock Stein on his statue that stands guard outside the main reception. And that means away fans, too.

Celtic supporters certainly played their part backing their team unconditionally. Celtic Park in full voice is one of the great occasions in football. “You’ll never walk alone” stretched from before kick-off, overwhelming Collum’s first whistle, and continued 23 seconds into the game. The fans’ tifo, “we will be your strength. Fear nothing,” read as an exhortation to their players.

Inevitably Callum McGregor was to the fore. Teams need strong leaders and Celtic’s captain led through word and deed, appearing on the right after 35 minutes and releasing the outstanding Matt O’Riley. And so the on-field show really began. O’Riley’s left foot had already hinted at damage to Rangers’ hopes, and his shot whistled past Butland.

READ MORE:  Clement offers Lundstrum defence but admits Rangers 'not good enough'

READ MORE:  Brendan Rodgers hails global support after derby win

McGregor immediately ran to the fans, punching the crest on his shirt, shouting “come on”. Rodgers, resuming his calm after a wild salute, called his captain over, had a quick confab. Rodgers is so experienced that he knows the vital importance of the manager always retaining his clear-eyed concentration.

He had to peer through a cloud briefly. A green flare was lobbed on the field, and smouldered away, until Butland eventually went over and threw it away.

The smell of cordite in the air, and Celtic had the scent of Rangers vulnerability. Daizen Maeda crossed, and John Lundstram, rushing back, diverted the ball past Butland. More flares, more mayhem.

But Rangers responded, and Cyriel Dessers poached a headed riposte. Then Lundstram’s competitive nature crossed the line. He launched himself at Johnston, catching him on the ankle, a shocking challenge. VAR did the right thing, Collum had a rethink, and yellow became red. Lundstram’s journey to the tunnel was followed by waves of “cheerio” and more.

Celtic should have brought some calm to the fray but O’Riley placed his weak penalty too close to Butland. Celtic became nervous, but held on, and the green wave rolled merrily back into town.