Canon Background
https://awoiaf.westeros.org/index.php/Jaime_Lannister

In-Campaign
In May of 288 AC Ser Jamie led a band of Lannister soldiers through House Jasper’s lands. He explained to Teddy Jasper that he had been dispatched by the King, under pressure from the High Septon, to ensure that construction of a Sept at the site of the Andal landing continue. It was agreed that miners from House Thorne’s mine would be conscripted as the main labor force, with some help from the soldiers. Utt and Olive also returned to oversee the Sept during and after construction. Jamie complained of boredom to Teddy mere days after arriving. He asked about recreation and Teddy did not offer much initially; he described getting into trouble as a boy but having matured. A sparring partner and a small tourney were then proposed, which warmed Jamie’s disposition. Sparring, a brief affair, with Ser Darron followed. Jamie made the seasoned warrior look like a page, breaking his sword and defeating him in a single blow.

In what became known as Ser Jamie’s Tourney in the region, in June of 288 AC, the eponymous Ser Jamie made quick work of each knight he faced. In the finals he bested Ser Darron in a single pass, showing all present that he has earned his reputation as a living legend. Jamie departed Snownook, bound the capital, within a week of the tourney’s end.