It has been a title race full of high drama and when the Premiership top two face off you know there will be plenty more to come.
Celtic extended their lead at the top of the table over Rangers in a highly-charged showdown at Ibrox.
The battle for the title has been so tight between the Glasgow rivals this season, so there was understandably a sharp focus on every decision made by the referee.
Experienced whistler Willie Collum took charge of the clash and had his fair share of big calls in Govan.
He has been the man in the middle many a time when these two Glasgow heavyweights have gone head-to-head, but the significance to the title race added extra pressure on his shoulders.
Record Sport runs the rule over Collum's big calls on a day of frenzied drama in Govan.
Carl Starfelt on Joe Aribo
With Rangers looking to reclaim their lead after Tom Rogic's equaliser, there were loud claims from the home crowd of a foul on Joe Aribo in the box from Carl Starfelt.
The Nigeria midfielder collected the ball in the box and the Celtic centre-back clipped the Rangers man as he changed direction.
The contact appeared to be inadvertent from Swede and the penalty claim was waved away by Willie Collum.
Verdict: Not a penalty.
Allan McGregor on Daizen Maeda
Ahead of Cameron Carter-Vickers' winner, Daizen Maeda burst into the Rangers penalty box and shrugged off the home defence.
Allan McGregor rushed out of his goal and narrowed the angle as Maeda looked to pull the trigger.
The striker collapsed under the challenge of the veteran stopper before the ball flew in the opposite direction.
But IFAB rules state a penalty kick is only awarded if the foul is "considered by the referee to be careless, reckless or using excessive force."
In this instance it appeared like both players had nowhere to go after a full-blooded challenge in the box.
Verdict: Not a penalty.
Cameron Carter-Vickers handball
After a neat pass from Ryan Kent to slip in Ryan Jack, the Rangers midfielder attempted to cross the ball into the Celtic box.
The ball then strikes the American defender on his upper left arm, followed by loud claims from the stands and the Rangers players for a penalty.
However the defender was fairly close to the ball and his arm was not raised.
It would be difficult to justify a spot-kick using the "unnaturally bigger" rhetoric used by IFAB.
Verdict: Not a penalty.
Ryan Jack and Giorgos Giakoumakis clash
The Rangers midfielder didn't take kindly to comments from the Greek striker claiming Celtic were better in every department.
Jack branded Giakoumakis "disrespectful" in the build-up to the Ibrox showdown and those tensions spilled over into a derby day flashpoint.
Giakoumakis flew into a late challenge on Jack well within the Rangers half, before the pair became entangled.
There were some handbags between the pair following the tackle, with the Celtic striker deservedly booked for the initial tackle.
Jack then appeared to lean a hand on the Greek frontman's head - something which would normally be defined by IFAB as "unsporting behaviour" under the subcategory of showing a "lack of respect for the game."
It left Giakoumakis furious and that action deserved a yellow card.
Verdict: Both players should have been booked.
Cameron Carter-Vickers on Connor Goldson
Connor Goldson was the target of James Tavernier's whipped corner into the box as the hosts pushed for an equaliser.
However, Carter-Vickers grasped onto Goldson's shirt as both players tussled to reach the ball. Kenny Miller branded it a "stonewaller".
Strictly following IFAB rules, a penalty kick should be awarded in any instance where a player "holds an opponent", so if VAR had been in play Collum may have had a second look at it.
But Collum was willing to let plenty go and the nature of the derby led to Goldson and Rangers left wanting not being awarded a spot kick
Verdict: IFAB rules may well have dictated VAR check if video replay was installed.
