Bones of 19th century prison ship inmates, which have been buried in mudbank, are not being uncovered. Human bones including skulls, teeth and vertebrae, litter the shoreline on grisly Deadman's Island off the coast of Sheppey, Kent. The uninhabited mudbank, which lies just 40 minutes from central London, was used as a mass burial ground for criminals who died on board prison ships, like those referenced in Charles Dicken's novel Great Expectations, in the 1800s.