‘Advanced tokamak’ (AT) scenarios were developed with the aim of reaching tokamak steady-state operation. They are designed to optimise the self-generated current, whilst also reaching sufficiently high plasma pressure to achieve optimal fusion reaction rates. AT scenarios exhibit non-monotonic to flat safety factor profiles (q, a measure of the magnetic field line pitch), with the minimum q (q min ) slightly above an integer value (q s ). This has the additional benefit of avoiding deleterious magnetohydrodynamic (MHD) instabilities. Nonetheless, it has been predicted that these q profiles are unstable to ideal MHD instabilities as q min approaches q s . These ideal instabilities, observed and diagnosed as such for the first time in MAST plasmas with AT-like q profiles, have far-reaching consequences like confinement degradation, flattening of the toroidal core rotation or enhanced fast ion losses. These observations motivate the analysis of the stability of advanced tokamak plasmas, with a view to provide guidance for stability thresholds in AT scenarios. Additionally, the measured rotation damping is compared to the self-consistently calculated predictions from Neoclassical Toroidal Viscosity theory.