For many years the residence, or sometimes styled the citadel, of the Quayle family.
The oldest part of the house dates from the early 18th century but its current elongated structure dates from c.1809 when George Quayle, hearing that extensions to Lorn House were being planned, determined not to allow the occupants to overlook his grounds. Accordingly he extended upwards to block out any views from Lorn House.
The house is built from local limestone which is somewhat porous -
hence the use of Manx slate to weatherproof the harbour facing
From 1802 the house served as the base for Quayle's Bank - currently it is used as offices but the boat house serves as the Castletown Nautical Museum whose prize exhibit is George Quayle's schooner Peggy.
Birthplace of Manx Banking Manx Life March/April 1978 p22 et seq has some description of the house (which was then on the market for £84,000 - the estate agernt's description ibid p8).
The Nautical Museum occupies what were the stable and boathouse of the older property.