Leyton Orient conceded four first-half goals and had Shadrach Ogie sent off late on as they suffered a disappointing defeat at the Breyer Group Stadium.

Northampton moved into an automatic promotion spot after their success in east London, while O's were left in 13th place with two games to go.

Paul Smyth fired straight at Liam Roberts after being played in by Theo Archibald on six minutes, with the visiting keeper producing a superb save to keep out Aaron Drinan's header moments later.

Lawrence Vigouroux denied Josh Eppiah at the other end, before Otis Khan's defensive header thwarted Sam Hoskins, and the O's keeper smothered at the feet of Louis Appere's feet on 17 minutes.

But Town opened the scoring seconds later with Mitch Pinnock arrowing a shot into the top corner and Ethan Coleman's downhead header from Smyth's corner was blocked midway through the half.

Pinnock shot just wide from the edge of the box, before Hoskins was booked for a foul on Smyth.

But Vigouroux had to make a fine save to keep out Eppiah, before Jon Guthrie doubled Northampton's lead at the second attempt after hitting a post on 31 minutes.

It was 3-0 on 37 minutes as Eppiah rounded Vigouroux and slotted into the net, with Shaun McWilliams booked for a poor challenge on Connor Wood.

Fraser Horsfall had his name taken for another cynical tackle, before O's hit back through Archibald in the first minute of first-half stoppage time.

But Eppiah quickly restored the three-goal cushion with his second to leave the home side with a mountain to climb in the second half.

Jordan Brown replaced Coleman during the break and netted a second O's goal on 50 minutes, as the ball fell kindly to him and he rifled past Roberts.

Harry Smith and Alex Mitchell replaced Ruel Sotiriou and Khan soon after as O's looked to force their way back into the game.

And Smith saw an effort saved, before Smyth's shot was cleared off the line by a covering Town defender.

Roberts got down quickly to save a header from teammate Ali Koiki on 63 minutes, with Smith heading just wide from Drinan's pinpoint cross soon after.

O's had penalty appeals for handball turned down on 70 minutes, with Jack Sowerby booked for fouling Smyth on the edge of the box.

But Archibald's free-kick hit the wall and he fired another chance over from 25 yards, after winning possession and cutting inside on 77 minutes.

Danny Rose was booked for a foul on Shadrach Ogie on 84 minutes, but the Orient youngster received his marching orders after reacting by putting his head towards the Northampton player, leaving the hosts to see the match out with 10 men.

Horsfall took the ball away from Smith as he looked to convert Drinan's cross two minutes from time, with the hosts unable to get any closer during six minutes of stoppage time.

Leyton Orient: Vigouroux, Wood, Smyth, Archibald, Khan (Mitchell 55), Drinan, Pratley, Beckles, Sotiriou (Smith 55), Ogie, Coleman (Brown 46). Unused subs: Sargeant, Young, Sweeney, Nkrumah, Brown.