At the beginning of the book, Malory places Arthur in London and in Carlion, the Caerleon of South Wales. Since he quickly moves Arthur to Camelot during the story of Balin, we must assume that his sources placed Arthur at Caerleon during his early reign, such as the story of the achieving of Excalibur. Malory has Arthur crowned in London at Pentecost and following the coronation, he established his knights in the region of London. Once done, he removed himself to Wales and held a coronation at Carlion and held a feast at Pentecost, probably the following year. This is similar to the medieval kings that passed from royal site to royal site during the year to dispense justice and secure the area, as well as the basic fact that no one area could sustain the royal court. By moving through each sub-ruler's lands, the king could collect part of his taxes in kind, providing food and drink for his court. At the Carlion Pentecost feast, the eleven kings defied Arthur. Malory immediately has Arthur back in London to hold a war council. No reasoning for this is clear unless Malory was indicating that the only region that Arthur held direct control over or in which he had a military power base was near London. Ban and Bors are sent for and the war ensues, culminating in the Battle of Bedegraine in the Lincoln area. Arthur and his allies then go to the relief of Leodegrance in Cameliard which I believe is in the area of the Severn. Another possibility is that Cameliard is the area of Gwent with Leodegrance court at the market town of Venta Silurum known now as Caerwent (which could be a possible Camelot, as its name could be translated in the English language as Winchester, Malory's Camelot). Arthur returns to Carlion and there he sleeps unknowingly with his half-sister Morgawse and has the adventure with Pellinore and the Questing Beast and the achievement of Excalibur.