Orient went into the game in second place but have now been leapfrogged as Brentford nicked a 1-0 win at the Matchroom Stadium to strengthen their ambitions for automatic promotion.
Read how it all unfolded in our minute-by-minute updates below.
11.46amMorning all! There's no early Championship game like normal this Saturday but there is a tasty tussle in the third tier as London clubs Leyton Orient and Brentford do battle. Team news coming right up...
11.48amORIENT XI: Jakupovic, Omozusi, Sawyer, Vincelot, Cuthbert, Cox, James, Lisbie, Mooney, Odubajo, Clarke
11.49amORIENT SUBS: Larkins, Batt, Lasimant, Bartley, Dagnall, Simpson, Ness
11.50amBRENTFORD XI: Button, Forshaw, Craig, Douglas, Donaldson, McCormack, Saville, Judge, Bidwell, Tarkowski, Trotta
11.50amBRENTFORD SUBS: Lee, Dean, Grigg, Dallas, Reeves, Yennaris, Adams
11.52amRighty ho. Just the one change for Orient as Kevin Lisbie returns in place of Chris Dagnall up top. Visitors Brentford make two alterations as Will Grigg and Jake Reeves drop to the bench, with Marcello Trotta and Adam Forshaw coming in.
11.55amClick here to see how the table looks ahead of today's matches. As you can see, Orient are just a point ahead of Brentford in second, two adrift of league leaders Wolves. You would argue that today's game is bigger for Orient as they have played two games more than their main promotion rivals.
12.01pmLooking at the two sides' form, both are enjoying good runs but it's Orient who come into this in slightly better nick.
12.04pmWhen these two last met back in September, it was Orient who triumphed 2-0, notching their eighth successive win to start the season. Recently it's Wolves who have been unstoppable to storm to the top of the pile. They've won a ridiculous nine in a row to take the lead.
12.07pmOrient chairman Barry Hearn described this game as the biggest of the season earlier, tweeting: "Biggest game of the season today so lets get behind the team from kick off to final whistle. We can do this!"
12.10pmPREDICTION TIME! Just five minutes until kickoff at the Matchroom Stadium. These two love to attack and under the East London sunshine today I am expecting goals. I reckon it'll finish 2-2, a result that Brentford would be happy with.
12.13pmHere come the two teams out of the tunnel. Orient are in their predominantly red home kit while Brentford have to don their yellow and blue away strip. Moments away from the off!
1 minKICKOFF! Madley blows on his whistle for the first time and Brentford get us underway!
3 minLittle to report in the early stages, with Brentford seeing most of the ball. Orient keeper and Hull loanee Jakupovic has just easily claimed Judge's cross from the left.
4 minBrentford top scorer Donaldson has the first shot of the game but it's a poor effort as he drags his shot well wide from the right of the area. Encouraging start from the visitors, though.
7 minForshaw escapes a booking after blatantly hacking down Omozusi, who was looking to start a counter-attack for the hosts.
10 min"Come on Brentford, come on Brentford!" sing the away fans as they win a corner but don't make the most of it by fluffing the short corner.
11 minCHANCE! First real sight of goal for either side as Lisbie holds off two defenders before teeing up Mooney. The hosts' top scorer should just blast it at goal but he goes for a delicate chip and gets it all wrong.
13 minOrient have now taken control and are doing all of the pressing. Cox's free kick was just met poorly by Lisbie at the back post before Vincelot's volley was deflected away for a corner.
14 minCLOSE! Mooney has another glimpse of goal in the box as the corner is headed his way inside the six-yard box. The striker can't turn it home and Brentford manage to hack it clear.
14 minJUST WIDE! Almost a stunning opening goal from Cox as he shifts the ball past a defender before unleashing a powerful low drive that zips wide of Button's right-hand post.
17 minBetter from Brentford down the left side as Bidwell links up with Judge before having his cross blocked by Odubajo. Good tracking back by the Orient man.
18 minBOOKING! The first yellow card is shown to Brentford defender Tarkowski, who slid in late on Cuthbert on the touchline.
21 minShaky defending at the back from Brentford as Tarkowski, who needs to be careful, shoves over Mooney. The hosts have a free kick right in the centre, just outside the D...
22 minSawyer tries to fire it under the wall Ronaldinho-style, but it doesn't make it through the yellow-and-blue barricade.
23 minSAVE! Brilliant surge from Saville in midfield before releasing Donaldson on goal. The Bees' top scorer could try to round Jakupovic but he attempts to prod it under the keeper's body but can't beat him. Best chance of the game so far.
26 minLovely link-up between the Brentford trio of Odubajo, Lisbie and Cox, with the latter firing low towards the near post where Button makes a comfortable save.
29 minSquabbles at both ends of the pitch as first Jakupovic is angry with Bidwell's late challenge before Cox and McCormack square up on the touchline. Madley keeps his cards in his pocket on both occasions.
33 minSHOT! Space opens up for Judge on the edge of the box and he shoots over the top when he could have fed Donaldson to his right. Poor decision from the Blackburn loanee.
12.51pmThere's an early Premier League game today as well and if you want to also follow Hull vs. Man City then open this link in a new tab!
38 minDear me, Douglas slices an aimless long ball out of play. No fluidity from either side at the moment.
40 minHANDBAGS! Big scuffle between the two sets of players with arms raised and plenty of pushing and shoving. You could argue that perhaps a red card might have been shown but just two yellows are brandished to Donaldson and Sawyer.
41 minLooking at replays of the incident, you have to say that Donaldson is lucky to escape with a yellow. He wasn't even involved in the initial commotion, unnecessarily jogging over and raising his arm into Sawyer's face.
44 minDecent pre-match atmosphere before the game, from Orient's Instagram page:
45+1 minSoon after two minutes of time are added on at the end of the first half, referee Madley has a chat with Brentford skipper Craig as tempers are really flaring up.
45+2 minGOAL! ORIENT 0-1 BRENTFORD (TROTTA)
45+2 minSeconds before half time was due, the visitors take the lead through Trotta's 11th goal of the season. Really well-worked from the Bees as McCormack passes into Forshaw, who cleverly backheels it into Trotta. His shot isn't all that powerful, but is right in the corner and Jakupovic can't get enough glove on it to push it wide.
45+3 minHALF TIME: ORIENT 0-1 BRENTFORD
1.07pmThe visitors go in ahead thanks to Trotta's strike just before the interval. It was a pretty even first half and a 0-0 scoreline at the break probably would have been right.
1.11pmAs things stand, Brentford are going to leapfrog Orient up into second place. It would be a HUGE result if they hold on as are going to have two games in-hand on the O's. They would go level on points with Wolves, who play lowly Shrewsbury later today and are surely going to make it 10 wins in a row.
1.15pmIf you scroll down on this page and look at the home and away tables, you'll see that it's Brentford who are top of the home and Orient top of the away. Not going that way today!
1.18pmHere come the two teams back out for the second half. Doesn't look like there's any half-time changes.
46 minCHANCE! Opening for the visitors and Trotta to double their tally, but the Italian's shot from Donaldson's cutback isn't well struck and blocked by a red shirt.
49 minOFF! BRENTFORD'S TARKOWSKI IS SENT OFF!
49 minWhat an idiot! Tarkowski gives Madley no choice but to send him off for a second yellow card by overrunning the ball and diving in late on Vincelot. The visitors' job of holding onto their lead is made so much harder now.
51 minBRENTFORD SUB: Warburton doesn't waste any time in making a change, taking off goalscorer Trotta for Harlee Dean. The former is key for the Bees going forward but isn't strong defensively so is rightly sacrificed.
53 minBOOKING! Brentford need to get their act together here as Forshaw becomes the next man to be cautioned for clattering into Cox.
54 minCox's free kick is poor but the O's dink the ball back into the box and almost get lucky with a ricochet before Brentford hoof clear. I'd be amazed if it stays 1-0. Either Orient's pressure will pay off or Brentford might nick a goal on the counter with Donaldson's pace and power.
58 minCHANCE! Neat interplay in the Brentford box as Vincelot flicks the ball onto Lisbie, who tries to shoot when not facing the goal and can only curl it well over.
61 minToday's attendance at the Matchroom Stadium is 8,335, with 2,597 Brentford fans making the trip across London. That's the biggest league attendance at Orient for 21 years.
64 minTrotta's strike at the end of the first half still separates the sides:
66 minPENALTY SHOUT! Oh that looks like Brentford should have a penalty! Saville makes his way into the box and Clarke appears to clearly tug him. Orient have got away with one there.
70 minORIENT SUB: Slade has to freshen things up and brings on Shaun Batt for Sawyer in an attempt to do so.
72 minSAVE! Button finally has to make a save as he uses his legs to block Omozusi's snapshot. The O's are unsurprisingly starting to pile on the pressure as Brentford can't help but sit back with their lead and with a man down.
75 minORIENT SUB: A change up front now for the home side as Lisbie, who has worked hard but had little reward, comes off for Chris Dagnall.
77 minMooney keeps the ball in at the back post before cutting it back to Cox, who looks to curl it into the far corner but gets way too much on it. Time running out for Orient.
79 minCLOSE! Brentford almost seal the win as Donaldson flicks a corner goalwards, it hits teammate Douglas just in front of Jakupovic, who somehow gets enough contact on it for the ball to go over the bar.
82 minDespite playing almost all of the second half with a man advantage, Orient haven't really done enough to get back in this game. Brentford worthy winners if it stays like this.
84 minSurely the home side, who are the division's top scorers, are going to have one last proper push for an equaliser though. No sign of that surge yet.
86 minBOOKING! Judge becomes the fourth Brentford player to be shown a yellow card for a late, high tackle in the middle. The Orient fans want a red card but that would have been really harsh.
88 minBrentford clear the ball from their own goalline before Batt appears to be brought down in the area by Saville. Again Madley isn't interested but that's probably now one penalty that each side should have had.
89 minORIENT SUB: Final throw of the dice from Slade as he sends on Marvin Bartley for James in midfield.
90+1 minOrient have FIVE minutes of time added on to find a winner. They don't look very likely to do so at the moment. A surprisingly limp display today.
90+3 minJudge and Donaldson do well in the corner to whittle away about a minute. Orient just completely out of ideas.
90+4 minOFF THE POST! Judge comes within inches of putting the result beyond doubt as Brentford break and the Blackburn loanee shoots past Jakupovic and against the near post.
90+6 minFULL TIME: ORIENT 0-1 BRENTFORD
2.11pmA fully deserved victory for the visitors as Trotta's goal proves to be enough even though they had to play most of the second half with 10 men. Orient were poor and simply didn't do enough to get level.
2.13pmIt's a massive three points for Warburton's Bees as they go two points clear of Orient in the automatic promotion places and still have two games in-hand on their rivals from the capital. Wolves now know that if they win their three games in-hand on Orient then they will go a huge 11 points clear of third place.
2.17pmAnyway, that's all we've got time for today. I'll leave you with the link for our live scores service, where you can find links for our other live commentaries this afternoon. Enjoy the rest of your Saturday!