Leyton Orient will play at Wembley for the first time in 15 years to contest a place in the Championship after beating Peterborough United 2-1 at Brisbane Road tonight.

Dean Cox gave Orient the lead on aggregate, thumping home his 16th of the season on the hour mark. Substitute Chris Dagnall made sure of Orient’s safe progression from close-range in the 87th minute, before in injury time, substitute Conor Washington pulled one back for Darren Ferguson’s side.

Russell Slade made one change, with Lloyd James taking John Lundstram’s place – James’ first start since the Good Friday defeat at Crawley Town.

Peterborough made just the one change too, Nathaniel Knight-Percival coming in for Kgosi Ntlhe and Craig Alcock moving to left-back.

Backed by a vociferous home support it was Orient who had the first noteworthy chance from a trademark Scott Cuthbert throw-in.

The Scottish full-back hurled the ball into the Peterborough six yard box where it was flicked on. With Bobby Olejnik caught in no-man’s land, David Mooney was unable to divert past the Posh goalkeeper from close range though before an almighty scramble ensued.

In the 11th minute Mooney tried his luck again, flashing a dipping half-volley narrowly over from distance following Kevin Lisbie’s knockdown.

Peterborough were gradually settling into their stride and skipper Tommy Rowe had their first shot on target in the 19th minute, drilling low into the palms of Jamie Jones from 20 yards.

Lisbie was unable to cap a flowing move in the 23rd minute, heading Cox’s cross from the left comfortably over at the back post.

Ten minutes before the break, James came as close as either side had in the opening 35 minutes.

Picking up the ball 35 yards from goal, the former Southampton midfielder took full advantage of the space in front of him and let fly, Olejnik getting down pull to push his effort around the post.

Peterborough had the first chance of the second period, Danny Swanson slashing well wide after being released by Nicky Ajose.

The visitors were on top and in the 54th minute, struck the post through Mark Little.

The adventurous full-back found himself in space on right-hand side of the penalty area, engineering enough of a gap to lash a wicked right-footed effort off the base of Jones’ far post.

Peterborough had begun like the home side after the break, but Orient wrestled back some of the momentum just a couple of minutes later.

Lisbie held the ball up on the left-hand edge of the penalty area, picking out Moses Odubajo in space on the edge but the livewire winger could only shoot left-footed into the arms of Olejnik.

In the 60th minute, Orient took the lead through Cox and Brisbane Road duly erupted.

A foul by Knight-Percival on Lisbie on the edge of the 18 yard box led to a free-kick which Cox saw blocked by ‘Boro bodies. From the follow-up the former Brighton winger lashed a volley through the crowd of bodies and past the unsighted Olejnik.

Cox tried his luck 60 seconds later, hoisting over from 20 yards with a curling effort.

Just minutes after his introduction as a substitute, Shaun Batt ought to have put the game to bed against his former side.

Mooney found Batt in space inside the Posh penalty area, but the gangly forward could only sweep his effort low into the grateful grasp of keeper Olejnik when one-on-one.

With just three minutes remaining Orient put the tie to bed as Batt made amends for his earlier miss by providing a telling assist.

Referee Mick Russell correctly awarded the O’s advantage and Batt immediately charged down the right-hand flank, taking his time to cut-back superbly for fellow sub Dagnall to jab past Olejnik and seal Orient’s path to Wembley.

In injury-time Peterborough set off Orient nerves as substitute Washington stabbed home from six yards following a scramble.

The O’s could have put further icing on the cake as the seconds ticked away, Dagnall curling comfortably over after Mooney’s cross-field pass found him in space.

Peterborough subsequently charged up the other end to earn a corner, but Alcock could only thunder his header over from six yards.

Leyton Orient: Jones; Cuthbert, Baudry, Clarke (c), Omozusi; Odubajo, James, Vincelot, Cox (Dagnall 73); Lisbie (Batt 68), Mooney.

Unused: Sawyer, Bartley, Dagnall, Lundstram, Simpson, Larkins (GK).

Peterborough United: Olejnik; Little, Knight-Percival (McCann 80), Baldwin, Alcock; Swanson (Washington 75), Payne (Isgrove 75), Bostwick, Rowe (c); Ajose, Assombalonga.

Unused: Ntlhe, McQuoid, Brisley, Day (GK).

Booked: Knight-Percival for a foul on Vincelot (49); Odubajo for a foul on Little (82).

Referee: Mr M Russell.

Attendance: 8,545 (1416 Peterborough).