This dataset contains GR6J (which stands for modèle du Génie Rural à 6 paramètres Journalier) modelled daily river flow time series for 95 river catchments in Great Britain and driving data (precipitation and potential evapotranspiration calculated from temperature) from the EC-Earth Single Model Initial Condition Large Ensemble (SMILE) climate model. The large ensemble is based on the EC-Earth Global Climate Model (GCM) v2.3 and is run for present day (equivalent to present day climate with observed global mean surface temperature for the period 2011-2015) and pre-industrial plus 2°C and 3°C global warming conditions. In total, they make up 2000 years of data for each global warming level (i.e. 16 ensemble members x 25 realizations x 5 years = 2000 years). All ensemble members are pooled to form a continuous 2000-year time series of meteorological input and daily modelled river flows. Full details about this dataset can be found at https://doi.org/10.5285/d966ae7f-a29b-4c57-835d-f4efd0d65c88