There is strong evidence in vivo and post‐mortem that [18F]AV‐1451 binds paired helical filaments of tau in Alzheimer's disease (AD).3, 4 The distribution and magnitude of in vivo tau binding correlates with AD staging,5 and recapitulates the anatomical distribution of focal onset forms including logopenic aphasia 6 and posterior cortical atrophy.7 Binding to tau in primary, non‐AD tauopathies is less well established, with inconsistency between in vivo PET findings and post‐mortem analysis in progressive supranuclear palsy.3, 8, 9. This evidence concerns the gene MAPT and Classical progressive supranuclear palsy.