Brownsea Island by third parties, is owned by the National Trust. Most of the buildings are situated near the small landing stage. The northern portion of the island is a Nature Reserve managed by Dorset Wildlife Trust and an important habitat for birds; this part of the island has limited public access. A small portion to the southeast of the island, along with Brownsea Castle, is leased to the John Lewis Partnership for use as a holiday hotel for staff, and is not open to the public. The island forms part of the Studland civil parish in the Purbeck local government district.
Brownsea Castle fallen into disuse. In 1726 the castle was converted into a private residence by William Benson, despite complaints from the town of Poole. Benson and the subsequent owners extended the original blockhouse to form a country house, landscaping the surrounding island to create ornamental gardens and lakes. The 19th century saw continued building work by the castle's occupants, including the entrepreneur Colonel William Waugh, who erected various Jacobethan-styled extensions. A serious fire in 1896 gutted the castle, which was restored by Major Kenneth Robert Balfour. The wealthy stockbroker Charles Van Raalte led a lavish lifestyle at Brownsea at the start