Peterborough 2 - 0 MK Dons (agg 4 - 3)
Craig Mackail-Smith grabbed his 34th goal of the season to take Peterborough into the League One play-off final.
With Milton Keynes Dons leading 3-2 from the first leg, Posh captain Grant McCann levelled the aggregate score when he curled in a free-kick.
Mackail-Smith tapped in the decider at the second attempt from close range after Dons keeper David Martin palmed George Boyd's shot into his path.
Peterborough will now play Huddersfield Town at Old Trafford on Sunday, 29 May.
No fewer than 109 goals had been scored at London Road this season before kick-off, at an average of 4.07 per game.
BBC Sport's Paul Fletcher
“It seems that Ferguson's failure at Preston has been to Peterborough's advantage, with Posh on the cusp of securing their third promotion in four seasons”
So it was no surprise that Peterborough, who made three enforced changes to the side who were beaten in the first leg at Stadium MK on Sunday, raced out of the traps looking for the goal they needed to level the aggregate scores.
Mackail-Smith saw a low shot pushed round his near post by Martin before the hosts found the breakthrough they wanted.
Gary MacKenzie fouled Lee Tomlin on the angle of the penalty area and McCann bent his free-kick over the wall and in at the near post, despite Martin's best efforts.
Grant Basey whipped over a low cross which Mackail-Smith and James Wesolowski just failed to convert, while Martin produced another smart save at his near post from Mackail-Smith as Peterborough, who were playing at a high tempo both with and without the ball, continued to have the better of proceedings.
But it was certainly not one-way traffic, and MK Dons served notice of their threat when Sam Baldock caused havoc in the home defence as he competed for MacKenzie's cross, and Daniel Powell stole in to smack a shot from 10 yards against the bar.
After surviving that scare, Peterborough threatened once more when George Boyd turned McCann's miscued shot goalwards but Martin was again equal to the effort.
They finally got their nose in front in the tie for the first time since Mackail-Smith's early opener at Stadium MK in the 54th minute.
MacKenzie and Sean O'Hanlon got in a terrible mess as they attempted to clear Tomlin's cross, presenting Boyd with a clear shot on goal.
Martin did superbly to save Boyd's drive, but could only divert the ball into the path of Mackail-Smith who, after seeing his initial effort blocked by the covering Luke Chadwick, slotted home at the second attempt.
Tomlin thought he had wrapped things up for Posh when he beat Martin with an angled drive, but referee Colin Webster inexplicably pulled play back for a foul on Boyd in the build-up.
And Peterborough almost paid a higher price when play swung to the other end as Baldock picked out the unmarked Angelo Balanta, who was denied a certain goal by an impeccably timed sliding challenge by Wesolowski.
The hosts reacted well to that let-off by going close again when MacKenzie deflected Tommy Rowe's goalbound shot for a corner, while Mackail-Smith was only denied a late second by the post.
MK Dons threw on Keanu Marsh-Brown and Lewis Guy in search of an equaliser but goalkeeper Paul Jones, starting only his second game for Posh because of first-choice Joe Lewis's knee injury, was relatively untroubled.
In fact, the Dons ended up fighting amongst themselves as Marsh-Brown and Stephen Gleeson, who was able to play after having his red card from the first leg overturned, exchanged words and pushed and shoved each other as their frustrations boiled over.
Peterborough hearts were briefly in mouths when Marsh-Brown fizzed in a low cross to Balanta, who should have done better then blast his shot over the bar before having his blushes spared by an offside flag.
Victory means Posh boss Darren Ferguson will return to Old Trafford to lead his side out against Huddersfield at the ground where he started his playing career, and where his father Sir Alex's Manchester United side will receive the Premier League trophy on Sunday.
Live Text Commentary
Full Time The referee brings the game to a close.90:00 +4:44
Craig Mackail-Smith is ruled offside. Indirect free kick taken by David Martin.90:00 +4:13
Handball by Keanu Marsh-Brown. Free kick taken by Grant Basey.90:00 +3:28
Craig Mackail-Smith takes a shot. David Martin makes a save.90:00 +2:39
Centre by Angelo Balanta, Paul Jones makes a save.90:00 +1:17
George Boyd decides to take a short corner.89:09
Mark Little produces a cross, Stephen Gleeson makes a clearance.88:15
Chris Whelpdale produces a right-footed shot from close range which goes wide of the left-hand upright.87:49
Free kick awarded for an unfair challenge on Lee Tomlin by Adam Clayton. Free kick taken by Lee Tomlin.87:09
Craig Mackail-Smith takes a shot. Save by David Martin.86:24
The assistant referee flags for offside against Angelo Balanta. Paul Jones restarts play with the free kick.85:37 Substitution
Substitution Lewis Guy on for Sean O'Hanlon.84:43
George Boyd decides to take the corner short.83:44
Free kick awarded for an unfair challenge on Craig Mackail-Smith by Sean O'Hanlon. Lee Tomlin takes the free kick.82:34
Ryan Bennett takes the free kick.82:34 Booking
Booking Keanu Marsh-Brown is shown a yellow card.82:25
Unfair challenge on James Wesolowski by Keanu Marsh-Brown results in a free kick.80:53
Inswinging corner taken right-footed by Lee Tomlin from the left by-line, clearance by Angelo Balanta.75:36
Outswinging corner taken right-footed by Lee Tomlin from the right by-line, clearance by Jabo Ibehre.75:36 Booking
Booking Dean Lewington is cautioned.
Free kick awarded for an unfair challenge on Lee Tomlin by Gary MacKenzie. Shot comes in from Grant Basey from the free kick.73:03
Jabo Ibehre is penalised for handball and concedes a free kick. Direct free kick taken by Paul Jones.72:04
Outswinging corner taken right-footed by Lee Tomlin, free kick awarded for an unfair challenge on Jabo Ibehre by Gabriel Zakuani. Free kick taken by David Martin.71:17
Corner from the right by-line taken by Lee Tomlin, clearance by Mathias Doumbe.70:47
Tommy Rowe takes a shot. Blocked by Gary MacKenzie.68:14 Substitution
Substitution Chris Whelpdale is brought on as a substitute for Grant McCann.64:54 Substitution
Substitution Jabo Ibehre comes on in place of Luke Chadwick.64:54 Substitution
Substitution Keanu Marsh-Brown comes on in place of Daniel Powell.62:21
Grant McCann has a direct shot on goal from the free kick.62:21 Booking
Booking Stephen Gleeson receives a yellow card.62:13
Foul by Stephen Gleeson on George Boyd, free kick awarded.60:38
Dean Lewington concedes a free kick for a foul on George Boyd. Grant McCann crosses the ball in from the free kick, clearance by Gary MacKenzie.59:44
Free kick awarded for a foul by Lee Tomlin on Gary MacKenzie. Direct free kick taken by David Martin.58:13
Mathias Doumbe fouled by Tommy Rowe, the ref awards a free kick. Direct free kick taken by Mathias Doumbe.56:40
The offside flag is raised against Craig Mackail-Smith. David Martin restarts play with the free kick.54:54
Angelo Balanta crosses the ball, Gabriel Zakuani makes a clearance.53:15 Goal scored
Goal! - Craig Mackail-Smith - Peterboro 2 - 0 MK Dons Craig Mackail-Smith gets on the score sheet with a goal from inside the six-yard box to the bottom left corner of the goal. Peterborough 2 (4)-(3) 0 Milton Keynes Dons.53:09
George Boyd takes a shot. Save by David Martin. Craig Mackail-Smith takes a shot. Luke Chadwick gets a block in.51:13
The ball is sent over by Grant McCann, Gabriel Zakuani takes a shot. David Martin makes a save.51:13 Booking
Booking The referee shows Luke Chadwick a yellow card for unsporting behaviour.51:07
Lee Tomlin fouled by Luke Chadwick, the ref awards a free kick.50:16
Angelo Balanta takes a shot. Save by Paul Jones.48:34
Free kick taken by Adam Clayton.48:34 Booking
Booking Lee Tomlin is cautioned.48:28
Lee Tomlin challenges Daniel Powell unfairly and gives away a free kick.46:38
Luke Chadwick gives away a free kick for an unfair challenge on Grant McCann. Grant Basey takes the direct free kick.45:15
Lee Tomlin has an effort at goal from outside the area missing to the wide left of the goal.45:01
The referee blows his whistle to start the second half.45:00 +2:11 Half time
Half Time The referee blows for half time.45:00 +1:43
Grant McCann takes a outswinging corner.45:00 +0:57
Angelo Balanta concedes a free kick for a foul on Mark Little. Direct free kick taken by Grant McCann.44:18
Mark Little gives away a free kick for an unfair challenge on Angelo Balanta. Dean Lewington takes the free kick.43:17
Unfair challenge on Dean Lewington by Lee Tomlin results in a free kick. Direct free kick taken by David Martin.41:26
The ball is crossed by Mathias Doumbe, Daniel Powell takes a shot. Save by Paul Jones.41:16
The ball is crossed by Mathias Doumbe, blocked by Ryan Bennett.39:43
Corner taken right-footed by Lee Tomlin from the left by-line to the near post, Angelo Balanta manages to make a clearance.38:06
Grant McCann takes a shot. David Martin makes a save.36:55
Sam Baldock gives away a free kick for an unfair challenge on Ryan Bennett. Direct free kick taken by Paul Jones.36:48
Daniel Powell takes a shot.35:42
Dean Lewington fouled by Craig Mackail-Smith, the ref awards a free kick. Dean Lewington takes the direct free kick.34:48
Lee Tomlin takes a inswinging corner from the left by-line to the near post, Angelo Balanta makes a clearance.33:49
Close range header by Gabriel Zakuani goes over the crossbar.33:29
Inswinging corner taken right-footed by Lee Tomlin played to the near post, clearance by Luke Chadwick.32:25
Corner taken by Lee Tomlin played to the near post, clearance made by Angelo Balanta.32:18
Craig Mackail-Smith takes a shot. Save made by David Martin.31:56
Foul by Sam Baldock on Gabriel Zakuani, free kick awarded. Grant McCann takes the direct free kick.28:32
The ball is swung over by Grant Basey.27:52
Mark Little crosses the ball, clearance by Gary MacKenzie.26:57
James Wesolowski takes a shot. Blocked by Gary MacKenzie.25:06
Unfair challenge on Mathias Doumbe by Lee Tomlin results in a free kick. Direct free kick taken by David Martin.23:22
Angelo Balanta takes a shot. Ryan Bennett gets a block in.23:15
The ball is sent over by Luke Chadwick, clearance by Gabriel Zakuani.20:28
Free kick awarded for a foul by James Wesolowski on Luke Chadwick. Dean Lewington crosses the ball in from the free kick.19:01
Corner taken right-footed by Angelo Balanta from the left by-line, Gary MacKenzie produces a header from deep inside the six-yard box which goes wide of the right-hand post.18:06
Corner taken by Dean Lewington, save by Paul Jones.16:53
Free kick awarded for a foul by Lee Tomlin on Stephen Gleeson. Sean O'Hanlon takes the free kick.12:15
Corner taken by Angelo Balanta from the left by-line to the near post, Paul Jones makes a save.12:04
Angelo Balanta takes a shot. Save by Paul Jones.10:04 Goal scored
Goal! - Grant McCann - Peterboro 1 - 0 MK Dons Grant McCann finds the net with a goal direct from the free kick from just outside the box to the bottom right corner of the goal. Peterborough 1 (3)-(3) 0 Milton Keynes Dons.8:50
Foul by Gary MacKenzie on Lee Tomlin, free kick awarded.7:28
Free kick awarded for a foul by George Boyd on Adam Clayton. Direct free kick taken by David Martin.6:20
Short corner worked by Lee Tomlin.6:11
Craig Mackail-Smith takes a shot. Save by David Martin.5:42
Free kick awarded for an unfair challenge on Grant McCann by Luke Chadwick. Grant McCann restarts play with the free kick.1:39
Sean O'Hanlon gives away a free kick for an unfair challenge on Craig Mackail-Smith. Grant McCann restarts play with the free kick.1:11
Foul by Lee Tomlin on Mathias Doumbe, free kick awarded. David Martin takes the direct free kick.0:00
The ref blows the whistle to start the match.
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