WASP-20b discovery data. Top panel: WASP lightcurve folded on the transit ephemeris. Middle panel: transit lightcurves from facilities as labelled, offset for clarity and binned with a bin width of two minutes. The best-fitting transit model is superimposed. Bottom panel: the radial velocities (CORALIE in blue, HARPS in green and HARPS covering the transit in brown) with the best-fitting circular Keplerian orbit model and the RM effect model.