Peterborough struck three goals in seven second-half minutes to bounce straight back to the npower Championship at the first attempt with a 3-0 win over Huddersfield.
Posh defender Tommy Rowe, striker Craig Mackail-Smith and skipper Grant McCann scored the killer goals in the 78th, 80th and 85th minutes to inflict on a stunned Town their first defeat in 28 league matches.
Rowe headed home McCann's free-kick, Mackail-Smith fired his 35th goal of the season two minutes later and McCann delivered the knockout blow with a fine free-kick five minutes from the end of normal time.
Victory marked a triumphant return to Peterborough for manager Darren Ferguson, who was sacked by Preston in December after leaving London Road in November 2009, and he has now led Posh to a third promotion in four seasons.
More than 35,000 Huddersfield fans looked on in disbelief as their season was shattered in seven devastating minutes, Lee Clark's side denied promotion in the cruellest of fashions by a first league defeat since December to leave the Yorkshiremen with nothing.
Peterborough had Clark's side on the back foot in the opening exchanges before Town skipper Peter Clarke's header, comfortably held by Posh goalkeeper Paul Jones, signalled a better spell for Huddersfield.
Gary Roberts' curling free-kick was saved at full stretch by Jones just before the break, while Benik Afobe's shot on the turn flashed just wide.
Town defender Gary Naysmith tripped George Boyd on the edge of the penalty area and from McCann's free-kick, Rowe flicked his header beyond Ian Bennett.
Posh fans had had no time to catch breath when Boyd stole clear down the left and his cut back into the area found Mackail-Smith, whose low shot took a slight deflection off Antony Kay and spun away from Bennett inside the far post.
Town were then dealt a knockout blow after Clarke felled Mackail-Smith, with McCann clipping home an exquisite free-kick to seal a stunning finale.
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