Leyton Orient's automatic promotion hopes suffered a major setback after losing 1-0 at home to ten man Brentford in front of a sold out crowd.
Brentford snatched a fortunate lead at the end of the first half when Marcello Trotta fired home for the Bees.
But the visitors were reduced to ten men early on during the second period when James Tarkowski was given a second yellow card for a rash tackle.
Orient struggled to take advantage of the extra man and were unable to find an equaliser as the Bees climbed above them into second place in League 1.
The O's made one change to the side with Kevin Lisbie recalled in place of Chris Dagnall in attack. Romain Vincelot recovered from his foot injury at Port Vale to keep his spot in midfield.
Orient's first opportunity fell to David Mooney after being set up by Lisbie but the Irish striker chipped his ambitious effort over David Button's crossbar.
The O's threatened again through Vincelot but the Frenchman's effort was deflected out for a corner. Orient kept the pressure on and Mooney was denied from close range by a defender.
Russell Slade's side went close again through winger Dean Cox but his fierce long-range strike flew just past the post.
Brentford had a golden opportunity on the break through Clayton Donaldson but the powerful forward was denied by an important touch from Eldin Jakupovic.
Orient created another opening through Lisbie as he flicked the ball onto Cox but his low strike was saved by Button.
The Bees put together a decent counter-attack which resulted in Alan Judge firing a shot over Jakupovic's crossbar.
The two sides got involved a brawl shortly before the break and the referee ended up showing a yellow card to Gary Sawyer and Donaldson.
Brentford snatched the lead right at the end of the first half when Adam Forshaw flicked the ball to Trotta and the striker struck a low shot into the bottom corner of the net.
The O's were handed a boost at the start of the second half when Tarkowski was shown a second yellow card for a rash challenge on Vincelot.
Orient were putting the pressure on their opponents and should have done better through Lisbie but he blasted high and wide.
Brentford were still prepared to attack on the break and Judge had an opportunity but the midfielder failed to find the target.
Slade made his first substitution when Shaun Batt was brought on in place of Gary Sawyer.
Orient had gone off the boil somewhat but the hosts created a great opening through Moses Odubajo but the winger's low strike was saved by Button.
The hosts made a second change when Dagnall was thrown into the action for the tiring Lisbie.
Cox should have done better when he cut inside but the winger blasted his effort high and wide of the target.
Brentford were not playing as if they had ten men and went close on the break through Forshaw but his effort was saved by Jakupovic.
Orient did not bombard the away goal late on and were finding it difficult to create chances against the Bees.
Batt had an opportunity from a header but his effort lacked power and was cleared off the line.
The hosts made their final change in the dying minutes with Bartley thrown on in place of Lloyd James.
It could have been 2-0 late on when Judge struck the post for the visitors.
There were five minutes of injury time for Orient to find an equaliser but the O's could not find a way through as Brentford clinched a priceless win which puts them firmly in the driving seat for automatic promotion.
Leyton Orient: Jakupovic; Omozusi, Clarke, Cuthbert, Sawyer Batt, 70); Cox, Vincelot, James (Bartley, 88), Odubajo; Lisbie (Dagnall, 75), Mooney
Subs not used: Larkins, Lasimant, Simpson, Ness
Brentford: Button; Bidwell, Craig, Tarkowski, McCormack; Judge, Forshaw, Douglas, Saville; Trotta (Dean, 51), Donaldson
Subs not used: Lee, Grigg, Dallas, Reeves, Yennaris, Adams
Referee: Robert Madley