The risk is particularly acute in children, who are subjected to intensive marketing of snack and fast-food products that are exorbitantly high in salt. The government's Scientific Advisory Committee on Nutrition (SACN) has recommended that children under seven years should consume an average of not more than two grammes of salt a day. Those between seven and 14 should consume not more than 5g.
"The furring of the arteries starts in early childhood, and children are now eating this appalling diet which is very high in salt," says MacGregor. "People are much less aware they are eating it, but it's all hidden in these processed foods. We are talking about foods that are 20-30% more salty than sea water."
As much as 80% of the salt in our diet comes from processed foods, but why do salt levels need to be so high? "Because it's completely inedible without it. It's totally tasteless," says MacGregor.
"It's to cover up," agrees Anton Edelmann, head chef at the Savoy hotel in London. "It makes up for poor ingredients. It also works as a stabiliser in some foods; it retains the moisture in the food, and keeps it a little bit longer."