  We present ALMA Band 7 polarisation observations of the OMC-1 region of the
Orion molecular cloud. We find that the polarisation pattern observed in the
region is likely to have been significantly altered by the radiation field of
the $>10^{4}$ L$_{\odot}$ high-mass protostar Orion Source I. In the
protostar's optically thick disc, polarisation is likely to arise from dust
self-scattering. In material to the south of Source I - previously identified
as a region of 'anomalous' polarisation emission - we observe a polarisation
geometry concentric around Source I. We demonstrate that Source I's extreme
luminosity may be sufficient to make the radiative precession timescale shorter
than the Larmor timescale for moderately large grains ($> 0.005-0.1\,\mu$m),
causing them to precess around the radiation anisotropy vector (k-RATs) rather
than the magnetic field direction (B-RATs). This requires relatively unobscured
emission from Source I, supporting the hypothesis that emission in this region
arises from the cavity wall of the Source I outflow. This is one of the first
times that evidence for k-RAT alignment has been found outside of a
protostellar disc or AGB star envelope. Alternatively, the grains may remain
aligned by B-RATs and trace gas infall onto the Main Ridge. Elsewhere, we
largely find the magnetic field geometry to be radial around the BN/KL
explosion centre, consistent with previous observations. However, in the Main
Ridge, the magnetic field geometry appears to remain consistent with the
larger-scale magnetic field, perhaps indicative of the ability of the dense
Ridge to resist disruption by the BN/KL explosion.
