Membranes offer exciting opportunities for more efficient, lower energy, more sustainable separations and even entirely new process options - and so are a valuable tool in an energy constrained world. However, high performance polymeric, inorganic and ceramic membranes all suffer from problems with decay in performance over time, through either membrane ageing (membrane material relaxation) and/or fouling (foreign material build-up in and/or on the membrane), and this seriously limits their impact. Our vision is to create membranes which do not suffer from ageing or fouling, and for which separation functionality is therefore maintained over time. We will achieve this through a combination of the synthesis of new membrane materials and fabrication of novel membrane composites (polymeric, ceramic and hybrids), supported by new characterisation techniques. Our ambition is to change the way the global membrane community perceives performance. Through the demonstration of membranes with immortal performance, we seek to shift attention away from a race to achieve ever higher initial permeability, to creation of membranes with long-term stable performance which are successful in industrial application.