The MHD code MARS-F is used to model low-n, low frequency, large amplitude Resonant Field Amplification (RFA) peaks observed in JET low pressure plasmas. The resonant response of a marginally stable, n = 1 ideal peeling mode is offered as a candidate to explain the experimental observation. These RFA peaks can potentially be used as an active MHD spectroscopy tool to predict the stability of the Edge Localised Mode (ELM).