As part of the search for alternative water supplies during the current drought conditions in eastern England,Anglian Water have been investigating the use of desalination as a potential future water resource. Anglian Water and Norit have designed and constructed a mobile pilot plant and have carried out a series of trials to establish the performance of the combination of hollow fibre ultrafiltration membranes followed by reverse osmosis to produce potable water from the North Sea. A small mobile pilot plant has been manufactured and installed at a side adjacent to the beach at Felixstowe in Suffolk. A series of site trials has been carried out to determine the potential of this two-stage membrane process for producing potable water from the North Sea. The pilot trials were carried out in two phases: the first phase used seawater abstracted from a beach well; the second phase was carried out using water abstracted directly from the sea. The results obtained demonstrate the water quality that can be achieved, the cost of water production and the performance of the specially manufactured RO membranes.