  Mixing in the $\Sigma^0$-$\Lambda^0$ system is a direct consequence of broken
isospin symmetry and is a measure of both isospin-symmetry breaking as well as
general SU(3)-flavour symmetry breaking. In this work we present a new scheme
for calculating the extent of $\Sigma^0$-$\Lambda^0$ mixing using simulations
in lattice QCD+QED and perform several extrapolations that compare well with
various past determinations. Our scheme allows us to easily contrast the
QCD-only mixing case with the full QCD+QED mixing.
