To be privately owned
The Castle can be visited
Blenheim Palace

Blenheim Palace, a castle in the English county of Oxfordshire, was built in recognition of military successes.
History+
The palace was constructed for John Churchill, the 1st Duke of Marlborough, during the reign of Queen Anne. It served as a reward for his military achievements in the War of the Spanish Succession, particularly for his victory in the Battle of Höchstädt on the Danube, known in English as the Battle of Blenheim. An exhibition within the palace commemorates Winston Churchill, a descendant of the Duke, who was born here in 1874. The construction of the palace, designed by Sir John Vanbrugh, was marked by disagreements between the architect and Marlborough's wife, Sarah, leading to cost overruns.
Source: Wikipedia · Licence: CC BY-SA 4.0
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 51.8414, -1.3610