I FINALLY FOUND THIS AGAIN: LLEON GAWR
(Source: Life of St, Werburgh, by Henry Bradshaw) (LINK)
I vaguely knew there was giant that was associated with the city of Chester, but I needed to look for where I got that idea from.
And it's here with this guy, Henry Bradshaw, a Chester-born clerk from Chester who made a chronicle of the patron saint of the city of Chester, St, Werburgh.
It's in this text, Bradshaw makes an offhand comment that the Polychronicon, by Ranulf Higden, claimed the founder of Chester was this supposed giant. And from what I could gather online, the Polychronicon never makes this claim, and seems to have originate solely from Bradshaw's pen.
It's likely that this purported mythical founder of Chester, is probably a back formation, derived from Chester's old Latin-Brythonic Name* "Caerlleon Vawr" meaning "Great Legion Fort" (which was Chester's strategic role for the Romans).
The reason why this caught my attention not only because is this about a giant named "Leo(n)" but also because of Chester's relative closeness to another location pertinent to Arthurian Legend.
Around ~40 kilometers south of Chester, in Shropshire (a day's ride away from Chester in Medieval Travel) is the Old Oswestry Hill Fort, an Iron age settlement that in local folklore is called Caer Ogyrfan/Caer Ogfran - Ogyrfan being the name of Guinevere's father in Welsh Mythology.
Local Folklore also claims that Caer Ogyrfan/Old Oswestry is the birthplace of Queen Guinevere. (Link) (Link)
Here is an excerpt from Giants of Wales, by Sion Dafydd Rhys
It probably helps that, in the French Vulgate, the kingdom of Cameliard has city called "Carhaix/Carohaise" (after the IRL Carhaix-Plouguer in Brittany, in typical medieval grasp of geography).
*(Chester's other name is Deva Victrix - "Victorious Goddess" - after the River Dee, where it was situatedin, and the it's tutelary goddess)










