Originally believed to have been designed by Anthony Keck, who had designed a similar property at Iscoed in Carmarthenshire, Whitson House had many Nash-inspired additions including the unsupported cantilever stone spiral staircase in the hall, similar to that of Ffynone Mansion at Manordeifi in Pembrokeshire, with an arched door frame underneath and plasterwork known to have been used at other Nash houses. There were also false plaster windows added to the ends of the adjoining pavilions which were typical of John Nash. In the same year (1791), Nash was working on his design for Newport Bridge and the lodge at Whitson Court is of a typical Nash design.