A last-minute penalty goal from Argentina's Martin Bustos Moyano secured Bayonne's promotion back to French rugby's top flight on Sunday, when they beat former European champions Brive 21-19 to edge the ProD2 final in a dramatic twist.
The Basque side return to the Top 14 after two seasons in the second-tier while the 1997 European Cup winners, who finished top of the table at the end of the regular season, will have another chance to claim their spot in a play-off against Grenoble, from the elite, next weekend.
Both sides exchanged penalty goals in a tense first half as Brive trailed 9-6 at the break.
Fiji centre Sevanaia Gaiala crashed over with half an hour to play to hand Jeremy Davidson's team a 13-12 lead.
The two teams slotted further penalties meaning there was one point between the clubs with five minutes to play.
Substitute Bustos Moyano stepped up with 10 seconds to play to kick the three points to clinch a surprise promotion for Bayonne.
Perpignan are already relegated from the Top 14 and reigning champions Castres will not defend their title after missing out on the end of season fixtures to last year's runners up Montpellier.
Toulouse, Clermont, Lyon, Racing 92 and La Rochelle make up the rest of the play offs which begin on Friday.