It was possibly whilst Cadoc was at Llangadog that he was annoyed by Sawyl Benuchel, who had established himself in the pleasant mountain basin of Cynwyl Gaio, where a bunch of rock, starting out of the level bottom that was once a lake bed, offered a suitable position for a caer, commanding as it did the entire basin. It bears the significant name of Pen-y-Ddinas, showing that at one time a stronghold occupied its crown, but the ruins of prehistoric fortifications have disappeared, as the hill has been converted into a rabbit-warren.
Below it stands Llansawel, leaving us to suspect that this ruffian in his old age turned saint and founder [...] The church is supposed to be dedicated to S. Sawyl Felyn ab Bledri Hir, and this may have been the chief who worried Cadoc, and later turned serious and founded the church [...]
Coflein notes that the area known as 'the Warren' was said to show remains of the fort at the turn of the 19th century. The hill has since been quarried.
A legend featuring Sawyl is connected with Carn Goch.