Forty minutes into an Old Firm derby that made you feel like you were riding a rollercoaster rather than sitting still watching a classic of its kind, Fabio Silva went down under a challenge from Alistair Johnston.

Johnston was correctly yellow-carded, but Silva's histrionics were a desperate over-reaction on a day, to that point, of utter under-performance.

Rangers were trailing 2-0 at the time - and they were lucky. In all departments in that opening half, they had been routed.

Celtic were sharp, hard-working and way too good. Daizen Maeda was giving James Tavernier an afternoon of his nightmares.

As the teams left the park at the break, the Rangers players were booed by their own people. At Ibrox, the vibe was not good.

You would have bet the house on Celtic winning and therefore taking a four-point lead at the summit.

Nothing would have been decided, but in psychological terms this would have been an awful jolt to the Rangers machine, a reminder that Brendan Rodgers is still the kingpin in this fixture no matter who Rangers put up against him.

As all those thoughts were forming, Philippe Clement was down in the dressing room talking to his players and telling them that they were not the team he had been seeing for the past five months.

Perhaps he had regrets about going with some of the personnel he went with - his wide attacking players were non-existent - and you could imagine him being a little shocked at the passive nature of his midfield in the face of a Celtic team who came to play, but also to battle.

His words must have been compelling because what we saw in the second half must place this game among the most memorable between these teams for a terribly long time.

In a half where everything changed, then changed again, then changed again, nothing has really changed, not at the top.

That is the irony. Celtic still lead and say their destiny is in their own hands, which it is. Rangers have a game in hand and say their destiny is also in their own hands, which is also true.

After a game that put the heart sideways at times, and made you dizzy with the frantic nature of the goals and the controversies, it seems bizarre to say that nothing has changed, but it hasn't. Not really.

'The show moves on in Glasgow circus'

This was arguably the biggest Old Firm game in a dozen years. Now the next one will be. The show moves on.

And what a show. Rodgers said the game could have been done by half-time and he was right. The dominance of the away team, even with Callum McGregor starting on the bench, was almost absolute. It was 2-0 going on 3-0.

Given the momentum Rangers had going into it, the one-sided nature was bamboozling. It was like the old days in Rodgers's first incarnation, when Celtic turned up with the only question being how many they would win by.

Ten minutes into the new half, Silva dived in an attempt to win a penalty and up in the Ibrox gantry that great Rangers soldier of the past, Stuart McCall, shook his head in despair.

A minute later, Silva went over again. And that is when the trumpet blasted and the drama started.

Booked for simulation. But hang on, here comes VAR. Cancel the yellow and let's have a penalty instead.

Rodgers said later that he firmly believes Silva dived. Every Rangers fan will say that there was contact. That is the Glasgow football shuffle right there.

James Tavernier banged away the penalty with aplomb for his 49th goal of the season, or maybe it just feels that way.

Where stood the title race now? Still Celtic's advantage. And still Celtic's lead after Cyriel Dessers' goal being ruled out for a foul in the build-up. Ibrox heaved.

Celtic faltered and on came McGregor, the break-glass-in-case-of-emergency option who has not played since the end of February.

Rodgers needed him to calm things down, to restore the composure of the first half that had been lost in the face of Rangers pressing high, chasing hard and finally believing in themselves.

Much of the pre-match narrative circled around McGregor's fitness, but he wasn't the only one deemed not fit enough to start. Abdallah Sima was another.

With eight minutes of normal time left, he found the Celtic net courtesy of a rare mistake by McGregor and a fortunate deflection. All level at 2-2.

We readied ourselves to acclaim Clement for the steel he has instilled in this team, for the comeback that few saw coming, for getting a draw that ensured a win over Dundee on Wednesday would get Rangers' noses in front of Celtic again.

Mentally, how would Celtic cope with losing a 2-0 lead? In the context of the title, was this draw a better draw for Rangers than it was for Celtic? You had to say yes, it was.

Then those thoughts went into the bin as Adam Idah scored to make it 3-2, a lovely finish planted in the corner of Jack Butland's goal.

For weeks and months leading up to the January transfer window, Rodgers had called out for quality recruits, an experienced cavalry to join the charge for the title.

Idah was welcomed into Celtic's bosom but it is fair to say the fans were expecting more. When the Irishman banged in that goal with a couple of minutes of normal time remaining, they would not have swapped him for anybody.

Celtic's rapid-fire response looked decisive. Again, the record books were being thumbed.

Rodgers' grip on this game was already vice-like and this was another story to tell. Celtic four points ahead again with Rangers to come to their place post-split. Ominous.

There was one last twist, one more plot shift. A week ago, Rabbi Matondo cut in from the left and rifled a shot high into the right-hand corner of Hibs' goal. Here, he cut in again and scored again.

Just as spectacular, just as jaw-dropping. Even more so, in fact. Ibrox shook to its foundations.

Clement said later that Rangers were more the winners on the day and, having trailed 2-0 and 3-2, you could not argue with him.

Rodgers, for his part, did not look all that perturbed. He knows that this was just the preamble with the biggest stuff yet to come.

Toe-to-toe they go into the business end. Thrillingly so.