Aquifer Thermal Energy Storage (ATES) is an underground thermal energy storage technology that provides large capacity (of order MWth to 10s MWth), low carbon heating and cooling to large buildings and building complexes, or district heating/cooling networks. The technology operates through seasonal capture, storage and re-use of thermal energy in shallow aquifers. ATES could make a significant contribution to decarbonising UK heating and cooling, but uptake is currently very low: eleven low temperature (LT-ATES) systems currently operating in the UK meet <0.01% of the UK's heating and <0.5% of cooling demand. The Wandsworth Riverside Quarter development in London is analysed as a successful UK case study. The UK has large potential for widespread deployment of LT-ATES, due to its seasonal climate and the wide availability of suitable aquifers co-located with urban centres of high heating and cooling demand. ATES could supply ca. 61% of UK heating demand, and ca. 79% of cooling demand with a 13%-41% reduction in carbon emissions for heating, and 70%-94% reduction for cooling, compared to equivalent ground- or air-sourced heat pump systems. However, problems with design and operation in some UK systems have caused sub-optimal performance. The UK can benefit from experience of both successful and unsuccessful deployments but these need to be more widely reported. Raising awareness, developing policies to encourage uptake, streamlining regulations and developing expertise are essential to unlock the potential of ATES technology in the UK, which requires engagement with policymakers, regulators, industry stakeholders and the general public.