A Roman fort originally occupied the site of the current Brougham Castle. The site of Brougham Castle was later taken by the Norman family of Vieuxpont to build their castle, the ruins of which can still be seen.
Vieuxpont's castle consisted of a stone keep, and service buildings, surrounded by a timber pallisade.
Nothing appears to remain from the Roman fort, and I have been unable to discover any archeological evidence that might link Brougham Castle to the era of King Arthur. The Norman Brougham Castle was abandoned in 1676, as the then owner appeared to have too many castles for his needs!
There seems little to substantiate a connection between Brougham Castle with King Arthur
Northern England Arthurian Sites