The tower has a crenellated stone parapet, in preference to iron railings on the gallery, and narrows in diameter above the half-way point.

Walker also pioneered, unsuccessfully, the use of a primitive water closet, comprising a specially designed drain exiting at the base of the tower.

The stepped design of the lighthouse may have helped water exit the closet, but surges of seawater made its use difficult during heavy weather.

[6] In 1922 Trwyn Du became the first Trinity House lighthouse to be automated,[7] when it was converted to unwatched acetylene operation.

In August 2019 Trinity House started trials of a new fog horn, stating, "The bell is activated by an ageing electronic striker mechanism which no longer provides the assurance of reliability which is needed.