Leopard Racing's Danny Kent held on to his Moto3 championship lead to secure the title at Valencia, despite a win for main rival Miguel Oliveira.
In doing so, Kent, 21, became the first British World Champion in motorcycle grand prix racing since Barry Sheene won his second 500cc title in 1977.
Kent only needed a 14th-place finish or higher at Valencia to finally take the crown that he had a shot at mathematically securing in every round since Motegi.
However, a difficult qualifying session left him 18th on the grid, while Oliveira, who needed to win to have a shot at the title, lined up in fourth.
And Kent's task was made harder when Oliveira stormed off the second row to lead into Turn 1, while the Briton himself moved up to 15th on the first lap - before taking the 14th spot on the lap after.
He subsequently progressed to 11th as the race went on as Oliveira battled Jorge Navarro, Romano Fenati and Kent's teammate Efren Vazquez for the lead.
The Portuguese rider seemed to finally establish a comfortable grip on the lead by the end of the race, yet he was passed by both Navarro and Vazquez with two laps to go.
However, he re-passed both bikes into Turn 1 of the final lap and went on to claim his fourth win from the last six races.
Yet, despite being passed by another teammate Hiroki Ono in the dying seconds, Kent finished ninth after a crash between Niccolo Antonelli, Vazquez and Fenati at the last corner and sealed the title.
In 2016, both Kent and Oliveira will both step up to Moto2, where they will be teammates at Leopard Racing.