A 'one system' approach to Britain's electricity networks is needed to ensure the lights stay on. Managing the challenges of decarbonisation, while maintaining security of supply and affordability for electricity customers, calls for radical and holistic thinking across the electricity system. The Institution of Engineering and Technology (IET) published a report in December 2013 entitled "Electricity Networks: Handling a Shock to the System", which recommends a 'systems architect' role to oversee the electricity system to help it adapt to meet the complex new requirements of a low-carbon economy. Decarbonisation means unprecedented change for our hitherto mature and stable networks over the next 20 years. They will have to cope with everything from two-way local power flows and less predictable generation to accommodating new demands like charging electric vehicles and powering heat pumps. All of this will have a profound impact on the electricity system.