It was five decades after crisps were invented that flavouring was applied: cheese and onion. Now you can buy varieties from bratwurst to spiced cola. But what inspired this explosion?

When she was a little girl in Essex in the 50s, Linda Miller would go over to her neighbour Barbara’s house every Friday night and together they would sit on the front step eating crisps. There was only one flavour widely available back then – Smith’s plain potato crisps, which came with a small blue sachet of salt that could be sprinkled over them. One Friday night, the two friends struck upon an idea. “We thought we’d invented a new crisp,” says 68-year-old Miller. Inspired by their weekly fish and chip takeaway, the pair “saturated” their plain crisps with a bottle of vinegar. “It was lovely, lovely – very tasty,” Miller says. “When salt and vinegar crisps came out, I remember thinking: ‘They’re not as good as what we do.’”

Crisps were first mass-produced in the early 20th century, but the first flavoured crisp was released only in the late 50s, after Joe “Spud” Murphy, the owner of the Irish company Tayto, developed a technique to add cheese and onion seasoning during production. Salt and vinegar crisps were launched throughout the UK a decade later, in 1967, when Miller was 16.