Ion Cyclotron wave (IC) assisted breakdown would be important for reducing risks to plasma initiation during the ITER pre-fusion operation phase under difficult vessel conditions. Hence, studies were performed at JET, at ITER relevant loop electric field  — and in a regime,  and , where plasma breakdown had not previously been achieved on JET ¾ to demonstrate the technique and provide a physics basis for extrapolation to ITER. IC assisted breakdown was achieved for the first time at JET at  and . The study covered a range of H₂ and D₂ gas prefill pressures and timings, fields, pumping conditions, and residual impurity levels. IC assisted breakdown was achieved for an increased and lowered range of vessel pressures and in the presence of increased in-vessel impurities. IC assisted breakdowns modified the wall pumping and consumes significantly larger amount of gas. IC assistance is much more robust with poor machine condition and can succeed with higher low-Z impurity content. It has no impact on impurity concentration in the developing plasma or on the initial current rise rate is found to scale with . The results and implications for ITER are presented.