Question: Who plays the legendary figure featured in Historia Regum Britanniae in the show Once Upon a Time?

Knowledge 1: Cherin
Cherin was a legendary king of the Britons as recounted in Geoffrey of Monmouth's "Historia Regum Britanniae". His father was King Porrex II and he was succeeded by his three sons in turn, Fulgenius, Edadus, and Andragius. [SEP] Knowledge 2: Porrex II
Porrex II was a legendary king of the Britons as recounted in Geoffrey of Monmouth's "Historia Regum Britanniae". His father was King Millus and he was succeeded by his son, Cherin.
Knowledge 1: King Arthur
The historical basis for the King Arthur legend has long been debated by scholars. One school of thought, citing entries in the Historia Brittonum (History of the Britons) and Annales Cambriae (Welsh Annals), sees Arthur as a genuine historical figure, a Romano - British leader who fought against the invading Anglo - Saxons some time in the late 5th to early 6th century. The Historia Brittonum, a 9th - century Latin historical compilation attributed in some late manuscripts to a Welsh cleric called Nennius, contains the first datable mention of King Arthur, listing twelve battles that Arthur fought. These culminate in the Battle of Badon, where he is said to have single - handedly killed 960 men. Recent studies, however, question the reliability of the Historia Brittonum. [SEP] Knowledge 2: Liam Garrigan
Liam Thomas Garrigan (born 17 October 1981) is an English theatre and television actor. As a youth he attended classes at Kingston upon Hull's Northern Stage Company and was a student at Wyke College, Kingston upon Hull. His first television role was as Nic Yorke in the BBC continuing drama series Holby City. He is best known for his roles as Ian Al - Harazi on the Fox series 24: Live Another Day and King Arthur in the ABC series Once Upon a Time and Transformers: The Last Knight.
Knowledge 1: Middle Ages
Chivalry and the ethos of courtly love developed in royal and noble courts. This culture was expressed in the vernacular languages rather than Latin, and comprised poems, stories, legends, and popular songs spread by troubadours, or wandering minstrels. Often the stories were written down in the chansons de geste, or "songs of great deeds", such as The Song of Roland or The Song of Hildebrand. Secular and religious histories were also produced. Geoffrey of Monmouth (d. c. 1155) composed his Historia Regum Britanniae, a collection of stories and legends about Arthur. Other works were more clearly history, such as Otto von Freising's (d. 1158) Gesta Friderici Imperatoris detailing the deeds of Emperor Frederick Barbarossa, or William of Malmesbury's (d. c. 1143) Gesta Regum on the kings of England. [SEP] Knowledge 2: Liam Garrigan
Liam Thomas Garrigan (born 17 October 1981) is an English theatre and television actor. As a youth he attended classes at Kingston upon Hull's Northern Stage Company and was a student at Wyke College, Kingston upon Hull. His first television role was as Nic Yorke in the BBC continuing drama series Holby City. He is best known for his roles as Ian Al - Harazi on the Fox series 24: Live Another Day and King Arthur in the ABC series Once Upon a Time and Transformers: The Last Knight.

Answer: Liam Thomas Garrigan