Investors with imagination are being given the chance to have their very own 'castle' for just £400,000, as long as they are willing to get there by sea.

Stack Rock Fort, located a short boat ride off the Welsh coast, is an opportunity to own a real piece of history.

The grade II listed building was built between 1850 and 1852, and then upgraded in 1859 with a new building that completely encased the original gun tower, real estate agent PurpleBricks said.

Made up of three floors connected by spiral staircases, the building was once armed with 16 guns and manned by up to 150 men. It was manned by a small consignment of men during the First World War.

The fort was one of a chain of forts designed to defend the middle part of Milford Haven and the Royal Naval Dockyard at Pembroke Dock against an invasion from France under Napoleon III.

“The island is currently uninhabitable but has unbelievable scope for development. Previous owners have enquired about the potential to turn the fort in to a commercial residence with links to the main land,” the agents said.