  We present the first high-precision photometry of the transiting extrasolar
planetary system WASP-7, obtained using telescope defocussing techniques and
reaching a scatter of 0.68 mmag per point. We find that the transit depth is
greater and that the host star is more evolved than previously thought. The
planet has a significantly larger radius (1.330 +/- 0.093 Rjup versus 0.915
+0.046 -0.040 Rjup) and much lower density (0.41 +/- 0.10 rhojup versus 1.26
+0.25 -0.21 rhojup) and surface gravity (13.4 +/- 2.6 m/s2 versus 26.4 +4.4
-4.0 m/s2) than previous measurements showed. Based on the revised properties
it is no longer an outlier in planetary mass--radius and period--gravity
diagrams. We also obtain a more precise transit ephemeris for the WASP-7
system.
