The work described within this report was commissioned by the Environment Agencies (comprising the Environment Agency of England and Wales, the Scottish Environment Protection Agency, and the Northern Ireland Environment and Heritage Service), as part of the on-going review of the impact of Sellafield discharges. The study used computer modelling to re-assess the radiological impact of past, current and future liquid discharges from Sellafield on the coastal communities surrounding the Irish Sea. The last comprehensive assessment using computer modelling was conducted in 1994 (Barr and Howorth, 1994). A suite of computer models has been used to simulate the transport of Sellafield liquid discharges through the environment and to calculate the resulting past, current and future radiation dose to specified population groups (coastal communities) around the Irish Sea. The period of time considered is from 1950 (the start of Sellafield operations) to 2050.