After Mary Ann remarried, the house was sold to Henry Grant in 1811 for the sum of £100,000 he lived in Gnoll House until his death in 1832. His son Henry John Grant remained at the Gnoll and sold a substantial part of the estate in 1857 shortly before his death.
The estate passed to his cousin Charles Evan Thomas who in 1881 demolished the east wing of the house and removed the castellated ornamentation because of tax liabilities.
During the next 40 years the house had several occupants and in 1923 Neath Borough Council took over ownership. The council found no permanent use for the house and its condition slowly deteriorated.
The house was used from 1925 for a number of years as a health clinic for Neath and Port Talbot areas. And during the second world war it was used for exercises and training of A.R.P. personnel.
The Gnoll Today
By 1957 the house was abandoned, therefore the only course of action the council could take was to demolish the house. Gnoll Estate fell into decline through the 20th century until restoration works started in 1984.
These works began at Mosshouse Woods and were then extended to the area of the former Gnoll house. In 1987 the Estate was granted the status of a country park by the the countryside commission, later the countryside council for Wales.
Today Gnoll Estate Country Park has undergone a number of restorations to capture the features that have shaped the history of the Estate.