The college consists of a number of buildings surrounded by extensive grounds. The main part is a three storey stone structure dominated by a massive stone tower. Numerous alterations and additions adjoining this nucleus have not always been consistent in either the 'style' or the materials of the original building (e.g. dormers in front elevation roof). However the sheer bulk of the original building provides a certain measure of consistency to the overall character typical of 19th century academic architecture. The Chapel has maintained its original integrity more or less intact although the scale of the large pitched slate roof to low stone walls contrasts with the opposite expression of the main school. To the rear of the main building, and in the annexe to the west, a different character altogether prevails with no underlying architectural acknowledgement of the unity of the complex. No comprehensive analysis of individual features has been made either internally or externally. The building complex and grounds have historic significance. The founding of the school extended the tradition of the Castletown Grammar School as the historic seat of learning on the island. Governor Smelt laid the foundation stone in 1830 and the college was opened by Bishop Ward in 1833. The fire of 1844 destroyed the priceless collection of Manx books and documents acquired from the Grammar School and kept in the college library. The complex including the grounds should be listed as a unit. 


This appraisal was undertaken prior to the existence of Registered Building or Conservation Area legislation on the Isle of Man in order to assess whether the complex was worthy of protection.  In the event, King William's College was placed on the Protected Buildings Register in 2001 (No. 185): the protected area only includes the main building, the chapel, and the cricket pavilion.  the war memorial outside the chapel was subsequently protected (No. 314).