Recent devastating flood events in the British uplands have focused attention on flood prediction and risk assessment, and highlighted one of the most important challenges facing river basin managers in the UK. The short instrumental record of river flow in the UK and the sparse distribution of gauges in upland river basins hamper predictions of future flooding. In this study, we compare and evaluate all lichen-dated flood deposits from UK upland river basins in order to assess changing flood risk over the last 250 years. Our analysis indicates that the incidence and size of extreme events have markedly decreased over the last 50 years, and may be at their lowest level since ad 1750. Occurrence of extreme upland floods over the last 200–300 years appears to be associated with negative North Atlantic Oscillation index values and significant non-stationarity evident in the historical flood series is shown to relate to decadal and multi-decadal scale climatic fluctuations.