Plasma rotation in tokamaks is of special interest for its potential stabilising effect on micro- and macro instabilities, leading to increased confinement. In MAST, the torque from Neutral Beam Injection (NBI) can spin the plasma to a core velocity ~ 300km.s -1 (Alfven Mach number ~ 0.3). Low density plasmas often exhibit a weakly non-monotonic safety factor profile just above unity. Theory predicts that such equilibria are prone to Magneto-Hydro-Dynamic (MHD) instabilities, which was confirmed by recent observations. The appearance of the mode is accompanied by strong damping of core rotation on a timescale much faster than the momentum confinement time. The mode’s saturated structure is estimated using the CASTOR code together with Soft X-Ray measurements, enabling the calculation of the plasma braking by the MHD mode according to Neoclassical Toroidal Viscosity theory. The latter exhibits strong similarities with the torque measured experimentally.