Bwystfil Y Bryn (Beast Of Bryn). It comprises of 3 separate runs a fun run, a 6.8 mile run and an extremely challenging 15 miler. Both 6.8 and 15 mile runs are very challenging and take place along the mountains of Margam and the Afan Valley, both runs take in some of the most breathtaking scenery in the country. You will run along routes that international runners use for endurance training prior to a major competition. The day will start with a fun run followed by both 6.8 and 15 mile competitors starting together.