Classical bovine spongiform encephalopathy (BSE) was first diagnosed in the United Kingdom in 1986. Scientific opinion is that classical BSE was caused by feeding feedstuffs to cattle that were contaminated with a transmissible spongiform encephalopathy (TSE) agent due to the inclusion of meat and bone meal. Scientific research has not identified any other definite vector of transmission and found no other potential causes, such as exposure to organophosphates. There is no evidence that it ‘spreads’ from animal to animal or between holdings. As a result of this scientific opinion, a ban on prohibiting the sale, supply and use of feeding stuff incorporating animal protein for feeding to ruminants was put in place in the UK in 1988. Following further scientific advice, in 1996 the ban was extended to prohibit the feeding of mammalian meat and bone meal, or any feeding stuff containing it, to any farmed animals. From a peak of over 37,000 cases in 1992 in the UK, there have been only 4 cases of the disease confirmed since 2014. This supports the hypothesis that classical BSE is a food-borne disease introduced by the inclusion of animal protein in feed, and that our BSE controls are working. It is still unknown which TSE agent caused the BSE epidemic (e.g. a scrapie agent from sheep or goats or an agent previously unknown in the cattle population that was recycled). Various transmission studies undertaken in GB and other countries failed to reproduce a BSE-like disease with TSE agents isolated from sheep or cattle other than classical BSE.