1. Centre for Water Systems, University of Exeter, Exeter, EX4 4QF, UK (E-mail: d.butler@exeter.ac.uk)
2. Department of Civil & Environmental Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK (E-mail: c.onof@imperial.ac.uk)
3. Thames Water Utilities, Gainsborough House, Manor Farm Road, Reading, RG2 5AN, UK (E-mail: a.p.hagger@thameswater.co.uk)