Full-time from Hayes Lane
As expected manager Neil Harris used the game at Hayes Lane to utilise his entire squad, using 21 players on the night against a well drilled Bromley side.
The first-half saw two summer signings make their competitive debuts for The Lions with goalkeeper Jordan Archer taking his place between the sticks and left-back Joe Martin slotting into a back four that initially included Mark Beevers, Sid Nelson and Shaun Cummings.
A wonderful cross-field pass from midfielder Shaun Williams picked out Fred Onyedinma in the opening minutes, but the teenage winger was just unable to control the ball and it bobbled out of play.
The home side broke the deadlock with their first really threatening attack on 10 minutes with a cracking finish from Moses Ademola, who latched onto a pass down the right flank and lashed the ball past Archer.
Millwall, cheered on by a considerable number of fans, got stronger as the opening half wore on and started to create chances of their own.
Thompson and Ed Upson, the outstanding player on the park, both tried their luck from distance but the former's effort lacked power and the latter's accuracy.
John Marquis had the best chance to level for The Lions when Williams' inch perfect pass picked out Onyedinma on the right flank, he in turn cut in and when his shot was blocked, the ball fell invitingly for Marquis who fired just over the bar from eight yards.
However, there was to be no denying the Millwall striker three minutes after the break when he stroked home the equaliser into the bottom left corner from the penalty spot after Aiden O'Brien had been fouled.
A second Millwall goal followed on 56 minutes; this time Onyedinma's trickery and persistence saw his first shot blocked by the home keeper and when he had a second stab at the ball his shot hit Ben Thompson virtually on the goal-line and flew into the back of the net.
Six substitutions followed for The Lions just past the hour mark with youngsters Mahlon Romeo, Kris Twardek, Kyron Farrell and Noah Chesmain making their first senior appearances for the team, followed shortly after by triallist Henrik Breimyr.
The multitude of changes unsurprisingly affected the attacking rhythm of the game, and The Lions played the last quarter hour down to ten men as Thompson went off after all subs had already been used.
With Millwall heading into the dying seconds of the game with a 2-1 lead and looking in control, the hosts hauled themselves level with a bizarre own goal from Tony Craig, making his third 'debut' after coming on as a half-time sub. There seemed little danger when Craig connected with a cross from the right, but somehow the defender's sliced clearance from 18 yards spun over his shoulder and looped beyond the reach of Tom King in the visitors' goal for the most freaky of levellers.