A second-half fightback earned Millwall a second home win in succession on New Year's Day as The Lions defeated Luton Town 3-1 in the Sky Bet Championship.
Sonny Bradley headed Luton into a first-half lead, but strikes from substitutes Tom Bradshaw and Connor Mahoney, plus a header from Matt Smith, comfortably wrapped up three points to begin 2020.
Gary Rowett made two changes from the side which defeated Brentford 1-0 on Sunday, with Shane Ferguson and Smith coming in for Murray Wallace and Bradshaw.
After retaining possession well in the opening moments, The Lions moved the ball forward and fashioned a cross through Mahlon Romeo, but the ball was just too high for the head of Smith.
Jed Wallace then caught former Lions midfielder Ryan Tunnicliffe in possession with eight minutes played, but his effort fizzed over the top of the crossbar. The winger then nearly provided an assist for Smith six minutes later, but the striker's nod down was tame and easily claimed by James Shea in the Luton goal.
The Hatters made their first foray into the Millwall penalty area on 16 minutes, but after Callum McManaman danced his way through a number of Lions players, his cross was cleared away.
Pelly-Ruddock Mpanzu then tested Bartosz Bialkowski for the first time on 21 minutes after some patient build-up play involving Alan Sheehan and Tunnicliffe, but the Pole was well positioned to parry before gathering at the second attempt.
Jed Wallace and Smith combined once more at the halfway point of the first-half, but again the header from the cross was just off target. James Bree then had a curling effort claimed by Bialkowski as the visitors began to gain a foothold, with Kazenga Lualua the next to try his luck from distance.
Four minutes from the break, Luton took the lead as Bradley glanced home from a Sheehan free-kick, completely unmarked.
Bradshaw was waiting in the wings to come on before that goal, but directly after it, manager Rowett decided to take off captain Alex Pearce for the frontman and switch to a more attacking formation - and it nearly paid dividends early in the second-half, but Jed Wallace's duo of long-range attempts were parried away by Shea.
A sustained spell of pressure just before the hour-mark led to a succession of corners being swung into the Luton box, but the final one ended with Smith heading over the crossbar from a Ferguson kick.
The Lions then fashioned another after Shea tipped yet another Smith header over the bar, with the home side then incredulous that a penalty-kick wasn't given after Jake Cooper's shirt was quite clearly nearly pulled off his back inside the area - referee Stephen Martin thought otherwise.
On 66 minutes a corner nearly led to a Millwall equaliser, but after a scramble at the back post involving Cooper, Smith and a number of Luton defenders, somehow, the ball was cleared out for a throw-in. Three minutes later, though, the scores were finally level as the bombardment paid off.
Referee Martin waved play on after Jed Wallace was fouled, but the winger picked himself up to receive O'Brien's pass and cross - Smith was waiting at the back post to nod into the path of Bradshaw, who tidied up from close range for his ninth goal of the campaign.
Just nine minutes later, just as it looked as though The Hatters were pushing forward again, The Lions took the lead and turned the game on its head. After a fantastic challenge from Romeo on Matty Pearson, Millwall raced forward and fed substitute Mahoney, who skipped past one tackle and rifled a superb hit past the despairing dive of Shea and into the net for his first goal for the club.
It only took another three minutes for The Lions to notch once more, as Luton's fragile back-line was unable to cope with the exciting Mahoney - the winger swinging in a pin-point cross on to the head of Smith, who got the goal his endeavour in attack throughout the afternoon had deserved.
Bradshaw then narrowly shot wide as the closing stages arrived, before a Mahoney free-kick looked destined for the net before it was blocked by the wall; Ferguson then slicing the follow-up wide.
The final whistle blew shortly after, starting the year - and decade - in perfect fashion for Millwall.
Millwall: Bialkowski, Hutchinson, Cooper, Williams, J. Wallace (M. Wallace 84'), Smith, Ferguson, Romeo, Pearce (Bradshaw 42'), Molumby, O'Brien (Mahoney 71'). Subs not used: Steele, Bodvarsson, Skalak, Mitchell.
Scorer: Bradshaw 69', Mahoney 78', Smith 81'
Luton Town: Shea, Cranie, Tunnicliffe, Bradley, Pearson, McManaman (Berry 62'), Mpanzu, Collins, Lualua (Cornick 75'), Bree, Sheehan (Bolton 82'). Subs not used: Stech, Shinnie, Jones, Butterfield.
Scorer: Bradley 41'
Referee: Stephen Martin
Attendance: 12,134 (945)