  The persistent discrepancy of about 3.5 standard deviations between the
experimental measurement and the Standard Model prediction for the muon
anomalous magnetic moment, $a_\mu$, is one of the most promising hints for the
possible existence of new physics. Here we report on our lattice QCD
calculation of the hadronic vacuum polarisation contribution $a_\mu^{\rm hvp}$,
based on gauge ensembles with $N_f=2+1$ flavours of O($a$) improved Wilson
quarks. We address the conceptual and numerical challenges that one encounters
along the way to a sub-percent determination of the hadronic vacuum
polarisation contribution. The current status of lattice calculations of
$a_\mu^{\rm hvp}$ is presented by performing a detailed comparison with the
results from other groups.
