Enrichment of nutrients in surface waters is a widespread problem in the UK impacting upon water quality, ecosystem biodiversity and recreational activities alike. Identification of spatial patterns of P loss at large enough scales to inform decision makers and catchment managers is vital if improvements in agricultural practice in particular are to be made. The P Indicators Tool (Heathwaite et al., 2003) provides a simple, transparent framework which identifies key indicators of P loss based on existing, national coverage databases of climate, soil type, topography and land use at the 1km^2 scale. Herein, it is demonstrated that available datasets can be used to identify patterns of P loss by adopting a layered structure which allows operation of the model at a range of scales (up to the national scale) and calibration of model parameters against observed data whilst permitting a clear view of all assumptions that are built into the tool. Results from five UK test catchments are presented highlighting "hotspot" areas of P contribution which may be further investigated for remediation purposes or as indicators of potential areas for land use change. The utility of this methodology as a policy support tool is demonstrated highlighting the key diffuse sources of P within catchment and laying the foundations for scenario-based modelling to aid P mitigation throughout the UK. Heathwaite, A. L., Fraser, A. I., Johnes P. J., Hutchins M., Lord E. &Butterfield D. (2003) The Phosphorus Indicators Tool: a simple model of diffuse P loss from agricultural land to water. Soil Use and Management, 19, 1-11.