We have applied the close binary system analysis program WINFITTER, with its physically detailed fitting function, to an intensive study of the complex multiple system Kepler-13 using photometry data from all 13 short cadence quarters downloaded from the NASA Exoplanet Archive (NEA) (http://exoplanetarchive.ipac.caltech.edu ). The data-point error of our normalized, phase-sequenced and binned (380 points per bin: 0.00025 phase interval) flux values, at 14 ppm, allows the model's specification for the mean reference flux level of the system to a precision better than 1 ppm. Our photometrically derived values for the mass and radius of KOI13.01 are 6.8 +/- 0.6 M-J and 1.44 +/- 0.04 R-J. The star has a radius of 1.67 +/- 0.05 R-circle dot. Our modelling sets the mean of the orbital inclination i at 94.35 +/- 0.14 degrees, with the star's mean precession angle phi(p) -49.1 +/- 5.0 degrees and obliquity theta(o) 67.9 +/- 3.0 degrees, though there are known ambiguities about the sense in which such angles are measured.