The original house on the site, Clytha House, was built by the
Berkeley family of
Spetchley Park in Worcestershire. It was subsequently purchased by William Jones the Elder, who constructed the gates and Clytha Castle. In 1955 he married Euphan Wardlaw-Ramsay, and from 1957 with the architect Donald Insall, they undertook the restoration of the wider estate including demolition of the substantial rear service building to leave the present square plan house. In 1972 they donated Clytha to the
National Trust in lieu of death duties, although the family retained a leasehold on the house where they still live today. The Clytha estate encompasses Monmouthshire's "two outstanding examples of late eighteenth century Gothic", the gates to the park and
Clytha Castle. Overlooking the house, on a prominent hill, stands the folly of Clytha Castle, constructed by William Jones the Elder in memory of his wife. Long attributed to
John Nash, recent documentary discovery has shown that it was designed by John Davenport, who also laid out the grounds, a "well-preserved (example of) a late eighteenth century landscape park". The original canal in the grounds by Davenport was extended in the early 19th century to create the present lake, the spoil from the excavations being used to create a raised platform for the new house. The park was further developed by
Henry Avray Tipping in the early 20th century. On the old
Abergavenny-to-
Raglan road stand the entrance gates, again reputedly by John Nash, who did undertake work in South Wales. A lodge is set to one side. They are earlier than the house, of 1797. The entry in
Mee's ''
The King's England'' suggests that the gateway came from the ruined mansion of
Perth-hir near
Rockfield but this is disputed. ==Architecture and description==