Towers on Lundy

Irish and Welsh legends contain numerous instances of  towers on  islands, the 'Tower of Bre?', the tower of Arianrhod, the tower under which the head of Bran is buried. 

Is there any evidence on Lundy for the existence of such a tower on Lundy? 

It is worth quoting the words of a visitor to these ruins not 50 years ago;-

"There are also the remains of those curious round towers, the origin and use of which are lost in antiquity. Some say they were strongholds of the Irish.....there is the finely cut stone .. held together not by the mortar of to-day or yesterday, but with a tenacious clay cement, hardened by fire. (We) were intrigued by this clay packing, older perhaps than the famous Roman brick, the secret of which has been lost." Etherton, Colonel P.T. & Barlow, Vernon - Lundy The Tempestuous Isle

'Chanter writes of other round towers on Lundy and conjectures they were introduced from Ireland by the Mariscos. Loyd however,considers this structure to be older....Chanter writes as if it stood several feet tall though it was probably robbed for stone.' The Isle of Lundy.

On the Ordnance Survey map, just south of the three- quarter wall and, significantly, above Knight Templar Rock,  are the remains of a round stone tower base.

The concept of an island with a tower at each corner seems much easier to grasp if you replace the word ' tower' with 'lighthouse'.