  An enhanced phenomenological model that includes isospin-symmetry breaking is
presented in this letter. The model is then used in a number of statistical
fits to the most recent experimental data for the radiative transitions
$V\!P\gamma$ ($V=\rho$, $K^*$, $\omega$, $\phi$ and $P=\pi$, $K$, $\eta$,
$\eta^{\prime}$) and estimations for the mixing angles amongst the three
pseudoscalar states with vanishing third-component of isospin are obtained. The
quality of the performed fits is good, e.g.
$\chi^2_{\textrm{min}}/\textrm{d.o.f} = 1.9$. The current experimental
uncertainties allow for isospin symmetry violations with a confidence level of
approximately $2.5\sigma$.
