Developing schemes for reducing the detrimental effects of sawteeth is an important objective in JET operation. To this end, minority hydrogen (with hH= nH/(nD+nH) 5-15%) ICRF heating and current drive at w 2wcH in deuterium plasmas has been used to reduce the sawtooth period and amplitude. By helping to keep the size of the m=3/n=2 neoclassical tearing mode (NTM) seed island smaller than a critical value and thereby delaying onset of NTMs, the ICRF scheme also allows a higher normalised beta, bN, and improved plasma performance to be obtained [1,2]. In the following, these experimental observations are modelled and elucidated.