  Lattice QCD with $N_f=2$ flavours of sea quark is used to explore the
spectrum and decay of a $J^{PC}=1^{-+}$ spin-exotic hybrid meson.
  We test lattice determination of S-wave decay amplitudes at threshold using
$b_1 \to \pi \omega$ where agreement with data is found. We find a hybrid meson
state at 2.2(2) GeV with a partial width to $\pi b_1$ of 400(120) MeV and to
$\pi f_1$ of 90(60) MeV.
