Harry Beck 's London Underground Map. In 1931, draughtsman Harry Beck realised that an electrical-circuit diagram was the ideal model for a new and improved map of the tube network. Two years later, the first version of a design icon was published. But why did he exclude everything at street level? And what dictated his choice of colour for each line? Minding the gap, Nicholas Crane finds out.
Director/Series producer Michael Waterhouse Nicholas Crane presents Coast on Friday at 9pm