Originally built as a defensive tower with a basement and two upper floors, it underwent a remarkable transformation around 1300 when the castle’s great hall was constructed. The tower was converted into a solar, essentially a private retreat for the lord’s family, taking on the characteristics of a tower house. This conversion involved significant architectural changes: a new ramped entrance was created from the southwest leading to the basement, whilst the original stairs to the upper level were blocked. Access to the two upper floors was now exclusively through the north corner of the Great Hall, though evidence of this connection has since been lost.

The transformation dramatically altered the tower’s interior layout. The old arrow loops were sealed, and the floor space was significantly expanded by breaking through the mural passages in the northwest and northeast walls, creating a large open area measuring 9.4m northwest to southeast and 8.4m northeast to southwest. This spacious chamber featured a fireplace on the southwest side and new window embrasures in each wall, though the southwest wall no longer survives. A D-shaped garderobe tower was added, projecting into the moat on the northeast side, with arches at its base allowing water to flow through. The upper level, accessed via newel stairs at the southern angle, boasted its own fireplace in the northeast wall and multiple windows, including two with seats in the southeast wall offering views over the moat.

Later modifications tell their own story of the tower’s evolving use. In the late sixteenth century, a fine octagonal pillar, likely salvaged from a suppressed church property, was installed in the basement. By the mid-seventeenth century, this lower level had been deliberately filled with layers of rubble and soil. The first floor saw its own alterations, with the southeast wall embrasure widened and a platform added outside, of which only the toothing stones remain as evidence. At the western angle, a chamber in the wall once provided access to both the solar’s parapet and the wall-walk of the western curtain wall, though only fragments of these features survive today.