The existing fort was built on the remnants of the old Chateau. Its white tower was originally built as a defence by the British in 1804 during the Napoleonic Wars, the builder was a local man, Thomas Henry from Clos du Valle The fort was named after Charles Grey, 1st Earl Grey, who was Governor of Guernsey from 1797 to 1807. It was made one of three locations in the island where a warning gun would be fired in case of invasion.