  In this paper, we present high-resolution HST/COS observations of the extreme
magnetic O star NGC 1624-2. These represent the first ultraviolet spectra of
this archetypal object. We examine the variability of its wind-sensitive
resonance lines, comparing it to that of other known magnetic O stars. In
particular, the observed variations in the profiles of the CIV and SiIV
doublets between low state and high state are the largest observed in any
magnetic O-type star, consistent with the expected properties of NGC 1624-2's
magnetosphere. We also observe a redshifted absorption component in the low
state, a feature not seen in most stars. We present preliminary modelling
efforts based on the Analytic Dynamical Magnetosphere (ADM) formalism,
demonstrating the necessity of using non-spherically symmetric models to
determine wind/magnetospheric properties of magnetic O stars.
