Britain's 2,300 miles of motorway are the backbone of the country, and without them, it'd probably all grind to a halt.

Hannah takes a drive to the National Highways control centre for the UK's busiest motorway to meet the team that keep these super-roads running 24/7. And she discovers how a mathematician with a passion for wild swimming, a Formula 1 legend and a 1960s road-sign revolution created the modern motorway.