About sixty years ago a respectable man declared that he was cutting a hedge between Trefas and Pant y Groes when a grey-headed old man came to him and told him that there was an underground way from Caerau to Pentre-Evan ; and that if he excavated a certain place he would find two hundred ” murk ” (? marks).
That’s quite a long tunnel but who cares.
From ‘The History of St Dogmael’s Abbey’ by Emily Pritchard (1907), who was actually quoting the Rev. Henry Vincent in Archaeologia Cambrensis, Oct. 1864.