Werthyr standing stone or erect monolith measures 3.1m tall, 1.6m wide and 0.5m high. It rises to a flat top with a distinct shoulder on the western side. In the nineteenth century there was said to have been a second similar stone with a 'huge' capstone resting on both. According to this account the additional stones were destroyed to the dismay of the country people who 'stood in great awe' of the monument. The presence of a capstone seems improbable, given the form of the 'surviving' stone. Several packing stones are visible around its base.

Standing stones such as this are often identified as prehistoric ceremonial or ritual monuments, although neither a more recent date nor a more mundane function can be ruled out.

Source: Rhys in Archaeologia Cambrensis 4th series 13 (1882), 237
RCAHM Anglesey Inventory (1937), 3

John Wiles 04.09.07