Fort Grey is a Martello Tower in Rocquaine bay on the west coast of Guernsey. It is now open as a local shipwreck museum, housing a number of salvaged artefacts from famous wrecks including MV Prosperity and Elwood Mead.
The rock upon which it is built was known by the name Chateau de Rocquaine (Castle of Rocquaine), and was supposed to be the locations of witches' sabbats. It is colloquially known as the "cup and saucer".