Dai Llewellyn was the Caerphilly Catapults’ most famous Quidditch player, known for his reckless and foolhardy style of play (QA7).
His biography, He Flew Like a Madman, was written by Kennilworthy Whisp (QA). Tragically, he was eaten by a Chimaera while on holiday in Mykonos, Greece; he was so well known that a national day of mourning was held for Welsh witches and wizards (QA7). The “Dangerous” Dai Commemorative Medal is awarded each season in his honour to the most reckless Quidditch player (QA7). The St. Mungo’s ward for treating magical bites is named for him (OP22).
Dai (Welsh) = "shines, " a nickname for David.
Llewellyn (Welsh) = from llwy "leader" + eilun "image" Llew is also Welsh for "lion," appropriate for such a bold player.