We are entering a new era of astronomical polarimetry, in which new and stringent observational constraints are being placed on the role of magnetic fields in star formation.   In this talk, I will present James Clerk Maxwell Telescope (JCMT) POL-2 polarimetric observations of the OMC 1 region of the Orion A filament, taken as part of the BISTRO (B-Fields in Star-Forming Region Observations) survey.  I will discuss modifications to the Chandrasekhar-Fermi method which allow estimation of plane-of-sky magnetic field strengths in the presence of a magnetic field showing large-scale, ordered variation, and will derive an estimate of the magnetic field strength in OMC 1.  I will discuss the energetic importance and evolutionary history of the magnetic field in the OMC 1 region, with particular emphasis on the interaction between the magnetic field and the explosive BN/KL outflow.