Brownsea Castle the castle also has four cannons, probably dating from the 17th or early 18th century. The castle is protected under UK law as a Grade II listed building. Brownsea Castle Brownsea Castle, also known historically as Branksea Castle, was originally a Device Fort constructed by Henry VIII between 1545 and 1547 to protect Poole Harbour in Dorset, England, from the threat of French attack. Located on Brownsea Island, it comprised a stone blockhouse with a hexagonal gun platform. It was garrisoned by the local town with six soldiers and armed with eight artillery pieces. The castle remained in use after
Brownsea Island was sold to Kenneth Robert Balfour in 1891. Following the introduction of electric lighting, the castle was gutted by fire in 1896. It was subsequently rebuilt, and in 1901 Balfour put the island up for sale. The island was purchased by wealthy stockbroker Charles van Raalte who used the island as a residential holiday retreat. During this time the castle was renovated and served as host to famous visitors such as Guglielmo Marconi. Robert Baden-Powell, a close friend of the van Raaltes, hosted an experimental camp for boys on the island in the summer of 1907. Brownsea was largely self-supporting,