53rd Trainer's Tournament

The 53rd Trainer's Tournament took place 5 years prior to the start of the story. In the year which this tournament was held, it was won by Phillip Robinson, and he later went on to defeat Jude and became the new Leader of the Elite Four, until he was defeated by Amethyst, and his leadership was usurped. 
How Phillip won his tournament is unknown, but it is safe to assume that he had outwitted his competitors, as he is the chief strategist of the Elite Four, and one of the smartest Pokemon trainers in the region. 
In Heartsong Symphony, it took place two years before the start of the story and is won by Rosaline. Category:PAL Competitions