Peterborough United's hopes of a quick return to the Championship were dashed last night, with defeat in their League One play-off semi-final.
After a 1-1 draw in the home leg, Posh, the perennial yo-yo club, knew they needed a win in East London to secure an immediate return to the second tier.
The two sides traded blows in a goalless first half - with top scorer Britt Assombalonga going closest for Peterborough, but it was Orient who made the breakthrough midway through the second half.
Dean Cox's free-kick was blocked by the wall but fell straight back to the winger, who made no mistake second time around.
Posh pushed hard for an equaliser but were hit on the break, with Chris Dagnall delivering what would turn out to be the decisive blow.
Conor Washington pulled a goal back in injury time to set up a grandstand finish, but it was too little too late, leaving Peterborough to contemplate a second season in League One.
Posh owner Darragh MacAnthony took to Twitter straight after the game to congratulate Orient and thank the 1,400 Peterborough fans who travelled to London.
Massive congratulations to @leytonorientfc on their victory. Thoroughly deserved win with attacking play. Good luck in the final.
To the 1,400 posh fans we let down tonight, you were magnificent as per usual & a credit to the club. Safe home!
But ultimately, it's been a frustrating season for Peterborough - albeit with the Football League Trophy in the bag and, after this result, the chance to defend it next season.