Salt is back in the News as the latest 'health hazard', but there must be 'moderation in all things'. Small amounts of dark chocolate are recognised as beneficial to the human brain and wellbeing; but sodium chloride or common salt is essential for life. So what is salt and why has it played such a significant role throughout human history? Empires were built and administered through a salt tax; trade depended upon salt; the word 'salary' is derived from 'salt'; and a good person may be described as: 'Salt of the Earth'. These five lectures will look at various facets of the fascinating history of this crucial and critical compound in life on this planet.