The farmhouse and out-buildings that stood on the site of the present building is demolished.
Warnham Court was built in 1829 in Elizabethan style to the design of Henry Harrison. Though asymmetrical in plan, it had symmetrical facades to west and south. On the south side a terrace gave views to the South Downs. The house was faced with stone dug on the estate, possibly from a quarry on the site of the later sunken rock garden on the west side, and in 1835 was said to have around 50 rooms.
The house is sold to Sir John Henry Pelly, a Governor of the Bank of England and Chairman of the Hudson's Bay Company.
The house is purchased by Charles Thomas Lucas
Between 1866 and 1877 large additions were made on the north side to the design of A. W. Blomfield, including new stables, a billiard room, and a clock tower; at the same time the east wing was heightened by two storeys. By 1877 the south terrace, with statues and trees, extended to c. 600 ft. (183 metres), while the grounds immediately round the house, which Lucas laid out himself, contained exotic trees and shrubs. In the later 19th and earlier 20th century the house contained many paintings and objects d'art,
The Jacobean-style stone gateway and lodge at the south-east entrance to the park is built. It is designed by Arthur Blomfield, the son of A.W. Blomfield the architect who designed the significant alterations to the building after Mr Lucas had bought the house.
December 1901
A fire broke out in the billiards room early on Christmas Morning and destroyed a number of valuable pictures, the principle one being Bonington's "Venice" valued at 5,000. The other pictures were "Views of London", David Roberts; "Village Smithy," Creswick; "Glint of Sunshine," Peter Graham. "Venice" was bought by Mr. C.J. Lucas when the Monroe collection was disposed of.