The crystal structure and charge transport properties of the prototypal oxobenzene-bridged 1,2,3-bisdithiazolyl radical conductor 3a are strongly dependent on pressure. Compression of the as-crystallized alpha-phase, space group Fdd2, to 3-4 GPa leads to its conversion into a second or beta-phase, in which F-centering is lost. The space group symmetry is lowered to Pbn2(1), and there is concomitant halving of the a and b axes. A third or gamma-phase, also space group Pbn2(1), is generated by further compression to 8 GPa. The changes in packing that accompany both phase transitions are associated with an "ironing out" of the ruffled ribbon-like architecture of the alpha-phase, so that consecutive radicals along the ribbons are rendered more nearly coplanar. In the beta-phase the planar ribbons are propagated along the b-glides, while in the gamma-phase they follow the n-glides. At ambient pressure 3a is a Mott insulator, displaying high but activated conductivity, with sigma(300 K) = 6 x 10(-3) S cm(-1) and E-act = 0.16 eV. With compression beyond 4 GPa, its conductivity is increased by 3 orders of magnitude, and the thermal activation energy is reduced to zero, heralding the formation of a metallic state. High pressure infrared absorption and reflectivity measurements are consistent with closure of the Mott-Hubbard gap near 4-5 GPa. The results are discussed in the light of DFT calculations on the molecular and band electronic structure of 3a. The presence of a low-lying LUMO in 3a gives rise to high electron affinity which, in turn, creates an electronically much softer radical with a low onsite Coulomb potential U. In addition; considerable crystal orbital (SOMO/LUMO) mixing occurs upon pressurization, so that a metallic state is readily achieved at relatively low applied pressure.