Operation Cauldron

Operation Cauldron was a secret biological warfare trial undertaken by the British government in 1952. Scientists from Porton Down and the Royal Navy were involved in releasing biological agents, including plague ("agent L") at sea off the coast of the Isle of Lewis in the Outer Hebrides and testing the effects of the agents on caged animals. In one test, a trawler sailed through a cloud of plague bacteria (Yersinia pestis) on its return from a fishing trip to the waters around Iceland, causing concern about a possible plague outbreak around its home port in north-west England. This event was successfully covered up by Churchill's government; the trawler Carella was apparently kept under covert observation until the incubation period had elapsed, with a naval medical team ready, but none of the crew fell ill.