  Magnetized plasma interactions are ubiquitous in astrophysical and laboratory
plasmas. Various physical effects have been shown to be important within
colliding plasma flows influenced by opposing magnetic fields, however,
experimental verification of the mechanisms within the interaction region has
remained elusive. Here we discuss a laser-plasma experiment whereby
experimental results verify that Biermann battery generated magnetic fields are
advected by Nernst flows and anisotropic pressure effects dominate these flows
in a reconnection region. These fields are mapped using time-resolved proton
probing in multiple directions. Various experimental, modelling and analytical
techniques demonstrate the importance of anisotropic pressure in
semi-collisional, high-$\beta$ plasmas, causing a reduction in the magnitude of
the reconnecting fields when compared to resistive processes. Anisotropic
pressure dynamics are crucial in collisionless plasmas, but are often neglected
in collisional plasmas. We show pressure anisotropy to be essential in
maintaining the interaction layer, redistributing magnetic fields even for
semi-collisional, high energy density physics (HEDP) regimes
