More than half a century ago, Calvert, along with her colleague Jock Kinneir, took on what he called “possibly the biggest graphic design job ever” – creating a new signage system for Britain’s roads. “Calvert was fresh out of the Chelsea School of Art (where Kinneir had been her tutor) when the pair were asked to design signs for the first motorway in the UK. Sleek, modern and made to signal “a common language” with Europe, they were colour-coded, easy...