There was a moment in the second half when Pep Guardiola paused in the midst of whatever torment routinely grips him during the course of a match to throw an arm around Ole Gunnar Solskjaer and briefly acknowledge the occasional absurdities of a life in this game.

The most famous manager in the world was watching his Manchester City team lose a grip on the Premier League title they have won for two seasons running with an aura of invincibility that has slipped badly of late.

They have dropped eight points in their last five games but it is hard to put just a numerical measure on a defeat like this, when at times the Guardiola machine looked slow and vulnerable and – worst of all for their manager – were beaten by a younger, braver side.

This was a magnificent derby game on the pitch, where it was played right on the edge. Whatever came from the stands, both sides reflected the great long-standing rivalry, and the standard was high. Later Guardiola would suggest that United’s counter-attacking style was less noble than his approach to the game, and that his team had dominated the ball. But these are the challenges that champions face and the gap to league leaders Liverpool is now an enormous one.

No club have ever won an English top-flight title from 14 points behind, as City now are from Liverpool, and Guardiola was reminded afterwards that this is the lowest points return that he has ever taken in his managerial career after 16 games of a season.