The possibility to apply the Ion Cyclotron Resonance Heating (ICRH) scheme with fundamental heating of the majority ions in tokamak plasmas is of significant scientific and practical interest. The subject is especially important for the understanding of its perspectives in ITER DT plasma. Results of the experimental studies of ICRH at the fundamental frequency of the majority deuterons in JET plasmas with near-tangential deuteron Neutral Beam Injection (NBI) are presented. 1D, 2D and 3D modeling of JET plasmas ICRH were performed before the experiments with the application of TOMCAT, CYRANO and PSTELION codes, respectively. This modeling indicated that several ITER relevant mechanisms of heating may occur simultaneously in this heating scheme: fundamental ion cyclotron resonance heating of majority D ions, parasitic impurity ion heating and electron heating due to Landau damping and TTMP. All these mechanisms were studied in JET experiments with a ~90% D, 5% H plasma including traces of Be and Ar. Up to 2MW of ICRH power was applied at 25MHz. Dipole phasing was adopted, most power being launched with |k||| = 6.6m-1. All experiments were performed with Ip = 2MA, ne(0) = 2.5 × 1019 m-3 and Rax = 2.97 m. In most of the discharges the toroidal magnetic field strength was 3.3T (plasma deuterons resonance layer at R = 3m, Be and Ar resonances at 2.69 and 2.72m, respectively), but in one it was equal to 3.6T (plasma deuterons resonance layer at R=3.27m, Be and Ar resonances at 2.96 and 2.99m, respectively). Experiments were performed both with nearly tangential (~60o with respect to the magnetic axis) as well as nearly perpendicular (~80o with respect to the magnetic axis) neutral beam injection, and either using 130keV or 80keV beams. Approximately 5MW of beams were used, not only to preheat the bulk plasma, but also because fast deuterons have their cyclotron resonance Doppler shifted away from the cold resonance at which E+ - the RF electric field component that governs ion heating - is small, the shift of the resonance yielding enhanced RF power absorption efficiency. The effect of fundamental ICRH was demonstrated in these experiments at JET. Direct ICRH of fast beam deuterons was measured by the neutral particle analyzer in the energy range 120-240keV and was also noticed by g-spectroscopy. Electron and ion heating (directly by waves and indirectly by collisional relaxation of resonant deuterons) was observed by several diagnostics. It caused an ion and electron temperature increase from Ti ~ 4.3 and Te ~ 4.5keV (NBI-only phase) to Ti ~ 5.5 and Te ~ 4.8keV (ICRH+NBI phase), respectively. Comparing energies and heating powers, no significant confinement degradation was observed during ICRH for the adopted RF power levels. By adding 23% of heating power (PICRH = 1.6MW / PNBI+OH = 7MW) the fusion power was increased at least by 35% due to ICRH.