The land ruled by King Leodegrance. Malory never defines where this region is but I believe that it is the area surrounding the Severn stretching either toward Glastonbury and Stonehenge or westward towards Gwent. Reasoning for this is based on the events that occur in relation to the war with Rience. Rience of North Wales has overcome the surrounding kings and has besieged Leodegrance. After defeating the eleven kings at Bedegraine, Arthur and his allies go to Leodegrance's aid taking about six days to march into the land. There are some difficulties as always with Malory. He seems to clearly state that Bedegraine is in the Sherwood Forest area but assuming that trained troops even in the Roman times generally travelled about 20-25 miles a day and Arthur's forces were not yet predominately horse, it stretches the point that they arrived in six days if we are talking about the lower Severn or the Summer Country. However, Arthur's forces arrive and they route Rience's army. Later in the war, we find Rience besieging Terrabil which was Gorlois main fortress in Cornwall. As Rience is declared as a king in the area of North Wales or Powys, he seems to be attacking lands to his South.
   The one possibility that I discuss elsewhere is that Cameliard is the area of Gwent with Leodegrance ruling from Caerwent. As some sources state that one of Arthur's battles as stated by Nennius was in the area of Carlion, this might lend more support to Cameliard being in the Gwent region. He gifts Arthur the Round Table which could easily be a confusion not for a table but for the amphitheatre in Caerleon and its fortress which probably still housed troops, in other words, he gifted Arthur control of Caerleon with its military force.
   Plus we also have the similarities of the names Cameliard and Camelot, region and main city?