Cheltenham 1 Grimsby 0
Steve Guinan brought the curtain down on English football being staged at the Millennium Stadium as his strike ensured Cheltenham’s return to Coca-Cola League One at the expense of Grimsby.
The Robins, one of the Football League’s youngest clubs, have spent the majority of their seven years as a league side in the basement division.
But Guinan’s second-half strike in this League Two play-off final encounter means they will return to the league they last occupied in 2002.
The victory could have been by a more comfortable margin but goalkeeper Steve Mildenhall saved well from a Grant McCann penalty, who also rattled the crossbar soon after.
It was cruel on Grimsby, who finished six points ahead of the Robins and were only denied automatic promotion when they conceded a late goal to Northampton while Leyton Orient defeated Oxford to snatch third place.
The Mariners recalled Michael Reddy to partner Gary Jones in attack while Junior Mendes moved to the wing.
Cheltenham, meanwhile, brought Stephen Gillespie in at the expense of Kayode Odejayi, who had to settle for a place on the bench.
Both sides were nervy at the start with possession often being wasted.
But Cheltenham had a golden opportunity to take the lead when a long ball found Gillespie, who headed it ball beyond his marker and raced unchallenged towards goal.
However, his second touch was too heavy allowing Mildenhall to rush out and do enough to divert the shot for a corner.
Soon after they were again clean through, this time with Guinan who – with only Mildenhall to beat – shot straight into the hands of the grateful Grimsby goalkeeper.
Grimsby, who had shown glimpses of nice football but had yet to trouble the Cheltenham goalkeeper, lost striker Reddy midway through the first half due to injury.
His replacement Gary Cohen cleverly beat the offside trap just after the half hour mark but he took one touch too many and the Robins soon cleared the danger.
But just before the break the Mariners finally forced a save from Shane Higgs when Cohen unleashed a low drive that the keeper had to palm away to safety before Andy Parkinson sent a dipping shot just over the bar.
Gavin Caines headed on target soon after the restart from the corner but it was not enough to trouble Mildenhall, who saved comfortably.
Cheltenham introduced Odejayi just after the hour mark for Gillespie as they looked to add a different dimension to their attack.
And immediately after they took the lead when a poor clearance from Grimsby eventually fell to Guinan on the edge of the box.
The much-travelled striker turned his man before curling a cross towards the goal – and the ball evaded everyone to nestle in the corner of the net.
Grimsby were saved by Mildenhall soon after when he produced a smart save from a Cheltenham penalty.
McCann was brought down in the Mariners box and referee Paul Taylor pointed to the spot.
The Northern Ireland international picked himself but his penalty was well read by Mildenhall, who pushed it away to safety.
McCann was then denied by the crossbar when he sent a smart shot from the edge of the box and Mildenhall was again on hand to prevent Brian Wilson heading in the rebound.
There were more goalkeeping heroics at the other end as the game entered the final 10 minutes when Junior Mendes crossed low into the box for Gary Jones, whose goalbound header was superbly blocked at point-blank range by Higgs.
That save proved to be pivotal as Cheltenham held on in the dying minutes to secure their promotion.