Sir Alex Ferguson could not have failed to notice the huge banner as he took his seat in the directors' box.
'Not In My Lifetime' proclaimed the sign, mocking Ferguson's infamous response when asked if Manchester City would ever find themselves above Manchester United.
Ferguson, 80, may have been a formidable manager, arguably the greatest of all time, but his bullish claim that City would never eclipse United while he drew breath has come back to haunt him.
City have finished above United every season since 2013, when Ferguson stepped down having secured the last of his 13 Premier League titles during his glittering Old Trafford reign.
Since then, City have won four League titles and are on course for a fifth after this comprehensive victory over their local rivals, one which exposed the huge gulf in class between the two sides.
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After Riyad Mahrez had plundered City's third goal, which gave Pep Guardiola's side the breathing space they needed, a carnival-like atmosphere broke out among the home fans.
City's supporters were in ebullient mood and went through their full repertoire of songs, with even those in the Tunnel Club seats – the most expensive in the stadium – joining in with the Poznan dance.
City revelled in mocking the plight of their cross-town rivals - and who could blame them?
After so many years in the shadow of the honours amassed by their neighbours, this is City's time, a fourth League title in five years now within sight for Guardiola's record-breaking side.
The one consolation for United fans is that such a chastening defeat may have killed off Liverpool's title hopes this season and prevent them from drawing level with them on 20 championship wins.
