Forming part of the Portsmouth’s Solent Strait, Spitbank Fort is perhaps the only private island in Great Britain to be protected by walls six meters thick. Completed in 1878, Spitbank – along with two other forts – was intended to protect the heart of the British Empire from invading troops. The threat of invasion never materialized, with the forts standing empty for years to come. Recently converted to a luxury hotel, Spitbank Fort has since been restored to its former glory, providing guests with a private island experience they’ll never forget. Book it now.