The "Data Assimilation Research Centre" (DARC) has recently been funded by the UK Natural Environment Research Council (NERC) under its Centre of Excellence Initiative in Earth Observation. DARC is a distributed centre, including effort from Reading, Oxford, Cambridge and Edinburgh Universities, the Rutherford Appleton Laboratory and a strong partnership with the Met Office. DARC will aim to convert the wealth of Earth System data into a self-consistent form that researchers can use for quantitative analyses and prediction. This presentation will expand upon the why, how and what of DARC.