High power combined NB+ICRF (H)D heating experiments have been carried out in the JET MKIIa divertor configuration, both in deuterium (DD) and in deuterium-tritium (DT) plasmas. Results from a wide range of RF injected power, up to 9.5MW, NB power up to 22MW, plasma currents, up to 4.2MA, and toroidal field values, up to 3.6T, show a clear improvement in electron temperature, DD reactivity and stored energy with respect to NB only discharges. High energy Neutral Particle Analyser (NPA) data show that acceleration of the NB injected Deuterons takes place at the second harmonic deuterium resonance. This is confirmed by numerical simulations with the PION code. Experiments have also been carried out in the (He3)D heating scenario. ICRF heating has been an essential ingredient in the DT experiments in the ELM-free Hot-Ion regime, contributing to the achievement of a record fusion power of 16.1MW and a record stored energy of 17MJ.