Of course the Normans who could quickly grasp any military advantage, saw the importance of this location, and under Robert FitzHamon [Robert fitz Hamo] built a castle on the site of the prior Roman occupation. Here, a "borough" was established by 1100 AD making those French speaking folks king of the mountain. All sorts of "settlers" were invited to this area, and it became one of the first "swinging doors" of Norman, to Saxon, to English occupation.
Glamogran it was to become. [Robert fitz Hamo became know as "conqueror of Glamorgan"] Divided into three ; West Glamorgan (Swansea), Mid Glamorgan (Rhondda), and South Glamorgan (Cardiff), it is shown geographically in the figure above. It is here that the first JONES surname appears in Wales 1496. I suspect this fact reflects the long history of this "swinging door".
[The photo above was taken by me in 1998. I am sure the area has changed since then, but the impact will remain the same...:-).]