The famous tower, isolated on the hilltop of Y Graig and a distance from the old town, continues to bewilder and enchant residents and visitors to old Llantrisant.

However, the origins of this lonely tower remains something of a mystery. Traditionally historians have viewed it as a windmill which Taliesin Morgan claimed was destroyed in a Welsh rebellion in 1280. The record refers only to two mills belonging to the Lord and these are Felin Fawr at Maesyfelin and Felin Fach or Gibbon’s Mill which is essentially the Castell y Mynach Mill in Pentyrch. 

However there were probably then, as there certainly were later other mills in private hands.  The reference to the town mill being burnt several times during insurrections may have been Felin Fawr. The town mill may also be the same one as identified by the Royal Commission as a mill site on the Clun just below the town and within the borough jurisdiction. There is no reference to a windmill whatsoever.

When considering its vantage point, distance from the town and the over all positioning of the tower, the likelihood of this being a windmill becomes less possible.

It was probably an auxillary tower to the castle, because it had a view of the main route through the Ely Valley. This viewpoint would have made it an ideal command post, allowing the local garrison to oversee the route and be aware of any would-be rebels.

The tower was already shown as 'an old tower' on Bowen's map of South Wales in 1729.