Anthrax is a rare disease caused by naturally occurring bacteria which can form spores that are fatal to humans and animals. During the Second World War, government scientists from Porton Down attempted to weaponise anthrax, creating a deadly strain that they then tested on Gruinard Island, an uninhabited remote site off the coast of Scotland.

This proved disastrous for Gruinard and, from 1942 onwards, people were forbidden from setting foot on the island. Signs were erected on the shore and the adjacent mainland, and Gruinard was dubbed The Island of Death or Anthrax Island.

This documentary reveals an extraordinary Scottish story from 1981, when a shadowy group called the Dark Harvest Commandos claimed to have landed on the island and removed 300lbs worth of infected soil.

They wrote a dramatic letter explaining and justifying their actions, which was sent to various newspapers and the BBC. In the letter, they explained their campaign to clean up Gruinard had begun with a package of island soil dumped outside Porton Down.

Nobody knew who they were or if they were serious.