There was a house at Gyrn by the late 17th century and in the early 18th century it formed part of the estates of the Mostyns of Cilcain. The house was sold to Thomas Hughes of Halkyn in 1750. The present house incorporates features from both the late 17th century and 18th century. The house was subsequently sold to John Douglas, a Holywell cotton manufacturer, who transformed the house into a castellated mansion in the period 1817-24. It is likely that this principally entailed remodelling the earlier house by adding a third storey, and addition of the projecting dining room at the N end and a picture gallery and attached tower at the S end of the house. The present plan of the house is shown on the 1839 Tithe map, the year of Douglas' death. Gyrn Castle was subsequently purchased by Sir Edward Bates, a Liverpool merchant and ship owner. Bates appears to have made only minor alterations to the house but added numerous outbuildings.

The principal rooms and main stairway are on the R side of the entrance, probably following the general plan of the C18 house, with the gallery on the L side beyond the smaller rooms of the 17th century house.

The entrance hall has panelling to the walls said to have been brought by Sir Edward Bates from his house at Beechenhurst, Liverpool, and a Jacobean style panelled ceiling. The fireplace has ornate panelling in Jacobean style continuing across the flanking niches. The rooms on the L side of the entrance retain spine beams retained from the late 17th century (and a marble fireplace inserted late 20th century). The picture gallery is top lit and has a 5-bay roof with moulded arched braces on corbels, and collar beams with queen posts. A flat ceiling in the centre has octagonal panelling. The roof has a moulded cornice. A plain black marble fireplace in the E wall has a wooden surround. The dining room, on the R side of the entrance hall, has a panelled wainscot, and foliage trails to a panelled ceiling (the room above the dining room has a similar plaster ceiling). The Classical doorcases incorporate pilasters and panelled doors. The wooden chimneypiece has double Ionic pilasters and an overmantel with a mirror and round-back niches. The fireplace is placed in the centre of 3 blind arches in the N wall. The stair hall, behind the entrance hall and dining room, has a full-height open-well 18th century stair, with turned balusters, 3 per tread, wreathed handrail and moulded tread ends. The quarter-turn service stair, behind the rooms with 17th century detail, has plain balusters.

Listed as a 19th century country house notable for its castellated style typical of the 19th century Picturesque movement, the result of remodelling an earlier house on the site.

Llanasa Tithe map 1839;
Cadw/Icomos Register of Parks & Gardens in Wales, PGW (C) 33;
Hubbard, Edward, The Buildings of Wales: Clwyd, 1986, pp383-4.

Associated with: Grounds & gardens (NPRN 86579)
Coach House (NPRN 308371)