Second-half strikes from skipper Paul Robinson and Steve Morison kept Millwall firmly in the race for automotic promotion with a hard-fought victory against Leyton Orient.
Patience certainly proved crucial for Kenny Jackett's men on an afternoon in which rivals Leeds United thumped eight-man MK Dons 4-1 and both Swindon and Charlton were held to draws at Wycombe and Exeter respectively.
The Lions now have two games to go, are one point behind Leeds with both teams locked on the same goal difference, but the Yorkshire outfit have scored 75 goals compared to Millwall's 73.
It is all set for a nerve-jangling final two games of the season, and for spells of this match the anxiety of the home support seemed to affect the players too.
Possession wise, Millwall enjoyed the majority of play as The O's seemed content to sit back and absorb the pressure.
And in a frustrating first-half, The Lions were unable to break through a resilient red rearguard.
For the opening 20 minutes the home side showed greater invention going forward.
Danny Schofield drilled a foot wide of keeper Jamie Jones' left-hand post following a piece of trickery by Neil Harris before Darren Ward floated a header from Chris Hackett's 10th-minute free-kick narrowly over.
Harris and Hackett created an opening for Marc Laird 60 seconds later, only for the midfielder to underhit his pass to the onrushing Schofield and the danger was cleared.
Schofield was inches away from opening the scoring on 12 minutes when he picked up the ball on the left, shook off a couple of challenges and let fly with a crisp 20-yarder that curled fractionally past the post.
Harris missed a gilt-edged chance to score on the half-hour mark when he latched onto Schofield's sliderule pass only to drag his shot agonisingly wide of the post.
Chopper went close again two minutes later with a spectacular overhead kick from Hackett's delivery whilst at the other end Adam Chambers' free-kick was fired straight at the wall but Millwall failed to clear, allowing Ryan Jarvis to get a shot in on goal which just went over.
Chambers had the first chance of the second half for Leyton Orient but he shot wide of David Forde's post six minutes after the restart.
Morison's tame header from close range three minutes later lacked power and also sailed wide.
The longer the game went without a goal, the tenser the atmosphere got, and in the 60th minute Jackett introduced Gary Alexander for Hackett.
Alexander's arrival against his former team saw Morison move out to a position wide on the right in place of Hackett.
The move certainly paid off with the crowd responding, and the players' doing likewise.
Jimmy Abdou went close with a thunderous shot from the edge of the area that just went wide on 64 minutes.
Six minutes later The Lions finally managed to batter their way through a wall of red shirts when Scott Barron's cross into the area was flicked on by the unfortunate Ben Chorley into the path of Robinson, who made no mistake with a low shot from eight yards.
The Lions skipper nearly made it 2-0 moments later when he headed Barron's corner narrowly over.
Orient were denied a leveller on 76 minutes when substitute Jason Demetriou's powerful shot was pushed behind by a sprawling save by Forde at full stretch.
However, it was Millwall who bagged a crucial second goal 60 seconds later when Alexander slipped a sublime pass to Barron inside the area and the defender was bundled over by Chambers for a penalty.
Harris quickly picked the ball up and looked ready to try his luck from the spot, but he then graciously handed the ball over to Morison, who promptly stepped up to smash home his 20th goal of the season - the first Millwall player to reach that landmark since Chopper himself in the promotion-winning season of 2000/1.
Harris was denied his 19th of the campaign when his goalbound back header was cleared off the line by Sean Thornton.
The Lions were left kicking themselves for switching off deep into stoppage time, enabling Chorley's header from a Demitriou corner to squirm over the line when the ball really should have been cleared.
Millwall: Forde, Smith, Barron, Abdou, Robinson, Ward, Schofield, Laird (Fuseini, 81mins), Harris, Morrison, Hackett (Alexander, 60mins). Subs not used: Sullivan, Frampton, Grabban, Grimes, Obika.
Scorers: Robinson (70mins), Morison (80mins, pen)
Leyton Orient: Jones, Chorley, Mkandawire, Chambers, McGleish (Pires, 86mins), Thornton, Daniels, Jarvis (Patulea, 81mins), Spicer ((Demetriou, 68mins) , Smith, Lichaj. Subs not used: Morris, Purches, Ashworth, Baker.
Scorer: Chorley (90+3mins)
Bookings: Smith (7mins), Chambers (79mins), Thornton (79mins)
Ref: Roger East
Att: 13,011 (away 1,021)