Earl Cowper, who later became
Lord Chancellor of
Great Britain, acquired the Cole Green estate c. 1700. He remodelled the estate in 1704 and made alterations to the house in 1711. The 5th Earl Cowper commissioned
Samuel Wyatt and then
William Atkinson to design a new house in a slightly different location in Regency-Gothic style; construction work started on site in 1806. Following the death of the
7th Earl Cowper in 1905, the estate was inherited by
Ethel Grenfell, Baroness Desborough and, after she died in 1952 with no heir, the estate was sold in lots by auction the following year, but there was no interest in the house itself and it was demolished between 1953 and 1954. The park contains the largest maiden (not pollarded) oak in the country, with a circumference of 7.6 metres. It is believed to have been planted by
Queen Elizabeth I. Acorns from the tree have been used as seedlings for notable oaks in other parts of the country, such as the
Prince Consort Oak in the
Forest of Dean.
Winston Churchill planted a sapling from the tree in the park and the tree can still be seen in the grounds. ==Panshanger Park and nature reserve==