  We have developed a new model for analysing light curves of planetary
transits when there are starspots on the stellar disc. Because the parameter
space contains a profusion of local minima we developed a new optimisation
algorithm which combines the global minimisation power of a genetic algorithm
and the Bayesian statistical analysis of the Markov chain. With these tools we
modelled three transit light curves of WASP-19. Two light curves were obtained
on consecutive nights and contain anomalies which we confirm as being due to
the same spot. Using these data we measure the star's rotation period and
velocity to be $11.76 \pm 0.09$ d and $3.88 \pm 0.15$\kms, respectively, at a
latitude of 65$^\circ$. We find that the sky-projected angle between the
stellar spin axis and the planetary orbital axis is $\lambda = 1.0^{\circ} \pm
1.2^{\circ}$, indicating axial alignment. Our results are consistent with and
more precise than published spectroscopic measurements of the
Rossiter-McLaughlin effect.
