Food sustainability is a vitally important topic, since the global food system is threatened on many fronts by the consequences of unsustainable practices. Food service, i.e. food prepared for consumption outside of the home, is a significant part of the food sector. This research considers the environmental sustainability of the food service sector in the UK. The study focuses on a canteen where the meal is kept warm for some time after preparation, assuming different recipes. Life Cycle Assessment (LCA) has been used to quantify the environmental impacts in the supply chain of this meal. To the knowledge of the author, this is the first LCA study in the UK food service sector. Eleven environmental impacts have been estimated following the CML 2001 impact assessment method, plus net primary energy demand. The results show that for six CML impact categories, including global warming potential, the greatest contributor to environmental impacts is the agricultural stage. For the remaining categories, impacts are spread more evenly throughout the supply chain.The results were compared with LCA results from literature for the equivalent ready-made or home-made meal. For nine out of eleven CML impact categories, the canteen meal had the lowest impact. This was mostly due to higher energy efficiency associated with cooking meals in large batches in the canteen and lower levels of food waste.Several recommendations for canteen operators can be drawn from the study. Reducing levels of food waste can reduce all impacts (in this study, by an average of 22% between best and worst cases). Replacing British tomatoes grown in heated greenhouses with Spanish tomatoes grown in unheated greenhouses can reduce impacts by an average of 46% in the categories of ADP (elements), ADP (fossil), AP, EP and GWP (100), but the additional transport required increases impacts in FAETP, HTP, MAETP, ODP, POCP and TETP by 14% on average. In all categories for which agricultural data for meat is available (ADP (elements), ADP (fossil), AP, EP and GWP (100)), the impacts per meal are highest for beef, pork and sheep meat, medium for chicken and lowest for faba beans and sunflower seeds (except for ADP (elements), where sheep meat outperforms chicken). On average in these five categories, choosing faba beans over beef can reduce impacts by 48%, implying that menu changes can contribute to environmental sustainability.Suggestions for further work include adding further data to the current LCA, integrating a nutritional analysis into the study, performing LCA for different types of meal and for other food service subsectors and considering social and economic aspects of sustainability in the food service sector.