As the teams filed out at the start and the Millwall fans belted out their raucous 'Let 'Em Come' anthem, some of the home fans waved a banner towards the away end.
'Have You Missed Us?' it read. Everyone knew the answer. They have learned to savour their notoriety in these parts and they were up for this one.
Old foes Leeds, top of the Championship, unbeaten in their first seven games had not conceded a league goal since the opening day of the season.
They brought 2,000 from Yorkshire and more than 3,000 more watched on a beam-back to Elland Road but there was little for them to cheer.
Millwall dominated from the outset and ought to have won by more than a scruffy late goal scored by Aiden O'Brien but one proved to be plenty.
Leeds were beaten for the first time this season, exactly what they deserved on the day.
Steve Morison thought he had opened the scoring in the seventh minute,
Conor McLaughlin's long-range effort was spilled by goalkeeper Felix Wiedwald and the rebound expertly whipped high into the net by Morison, who posed to show 2,000 away fans the back of his shirt.
An offside flag was up and the goal ruled out, which did not go down well with home fans in the Dockers Stand, who targeted the assistant referee with missiles and the game was paused more than once to collect the offending items.
Millwall dominated without finding the net. Jed Wallace fired wide and both Morison and Shaun Williams forced saves from Wiedwald as half-time approached.
Thomas Christiansen made two half-time changes but the pattern did not alter.
Wiedwald stuck out a boot to foil Shaun Hutchinson after Leeds failed to clear a corner and Wallace hit a post, a crisp strike on the half-volley from 20 yards.
Fred Onyedinma miscues with a header in front of goal and Hutchinson header cleared off the line by Conor Shaughnessy
When Wiedwald saved from Morison, it seemed as if it would be one of those days. Then O'Brien pounced, 17 minutes from time, set up by Onyedinma.
It was the first goal conceded by Leeds in more than 10 hours of Championship football.
Leeds finished the game with 10 men. All the subs were on when Pontus Jansson damaged a hamstring and limped off.
George Saville missed a glorious opportunity for a second but no-one cared.
Leeds have lost their last four visits to the New Den and haven't scored a goals in any of them. They have not missed Millwall one bit.