This final OPAL analysis of hadronic and leptonic cross-sections and of leptonic forward-backward asymmetries makes use of the full LEP1 data sample. The parameters of the Z are determined in a model-independent way. Our results are consistent with lepton universality and with the vector and axial-vector couplings predicted in the SM. A fit yields m_Z, G_Z, sigma_0h, Rl, and A_fb^0l. Transforming these gives a measurement of the ratio between the decay widths into invisible particles and into a single species of charged lepton. Attributing the entire invisible width to neutrino decays, this translates into a measurement of the number of light neutrino species, N_nu = 2.984 +- 0.013. Interpreting the data within the context of the SM allows the mass of the top quark, mt = 162 +29-16 GeV, to be determined through its influence on radiative corrections. Alternatively, utilising the direct external measurement of mt leads to a measurement alpha_s and the Higgs boson mass.