George Thomas Clark, Mediæval Military Architecture in England…
“ The main strength of a tower of this character was passive, the loops and windows counting for nothing in the defence, but no doubt the battlements had a rampart walk, and the roof, therefore, was either flat, or if conical, sprang, as at Coucy, Coningsburgh, Pembroke, and Marten’s Tower at Chepstow from an inner wall. Nothing can be more senseless than, as some modern architects have done, to cover these towers with a conical roof springing from the outer wall, which thus could not be defended in the only way possible with such structures, from above. ”
