For one carefree moment, Pep Guardiola forgot himself and simply enjoyed watching Erling Haaland and Kevin de Bruyne do what Erling Haaland and Kevin de Bruyne do.
But as his men continued to celebrate De Bruyne’s opening strike, the Manchester City manager soon remembered what he was there for and called Ederson over for a comically animated b******ing on the touchline.
What the Brazilian goalkeeper had done wrong is anybody’s guess but this was a night when Guardiola had to be ranting at someone around the clock.
How fourth official Craig Pawson did not take a leaf out of the Constantine Hatzidakis book and accidentally chin Guardiola was a masterclass of self-restraint.
A minute or so prior to De Bruyne’s nice finish, Guardiola had volleyed a dozen bottles of energy drink from their position and plonked himself theatrically down on top of an ice bucket.
Sometimes, you have to wonder if it is all for show, all part of the act, all designed to rev up the crowd.
But, of course, it isn’t. Guardiola’s intensity is, quite simply, off the scale.
Being a big name, he frequently gets away with being over the top and that is inexcusable. How he escaped sanction during this contest is a mystery.
From where I was sitting, Guardiola appeared to lay hands on Pawson at one stage and someone at the FA might want to take a look.
There is no doubt that Guardiola gets an easy ride from officialdom - maybe they enjoy his football too much.
But if you do want to indulge Guardiola and overlook his indiscretions, you can only marvel at how he has maintained this level of intensity for so long.
Remember when the common wisdom was that Guardiola would do three years in the Premier League - tops - and then need a sabbatical to recharge his batteries/calm down a bit?
Well, almost seven years on from his arrival at the Etihad and he was as animated in this match as he has been for any game during that time.
And the truly astonishing thing is that while Guardiola might look like a man who is completely out of control, he produces football teams that could not be more in control of what they are doing.
Using Haaland for out-ball purposes was clearly in the game plan and led to that early De Bruyne hit - a breakthrough that came, ironically, as a direct result of Arsenal’s high press.
In the second half of this season, Guardiola has been fortunate to have very few, if any, serious injury concerns.
Without the depth City have got, one key absentee can fundamentally undermine a team like Arsenal and that key absentee is William Saliba, exposing Rob Holding to a night that will - his consolation goal aside - haunt him for a long time.
In an Arsenal jersey, he was not alone because they were simply blown away by an extraordinary footballing force … led - for all his faults, histrionics and dissent - by an extraordinary manager.
