There are more likely sites in the Mendips or Wales, but... as the M4 wasn't built for the next 5,000 years, chances are it was mined locally.
თმა გვპჲწრნთ მვჟრა გ მვნეთჟ თლთ სვლჟ, ნჲ მნჲდჲ გვპჲწრნჲ ეა ვ ეჲბთგანჲ რსკ.