  We explore the decay of a vector meson to two pseudoscalar mesons on the
lattice with $N_f=2$ flavours of sea quark. Although we are working with quark
masses that do not allow a physical decay, we show how the transition rate can
be evaluated from the amplitude for $\rho \to \pi \pi$ and from the
annihilation component of $\pi \pi \to \pi \pi$. We explore the decay amplitude
for two different pion momenta and find consistent results. The coupling
strength we find is in agreement with experiment. We also find evidence for a
shift in the $\rho$ mass caused by mixing with two pion states.
