The cross-section ratio R_(uds) = sigma(e+e- -> u-ubar, d-dbar or s-sbar)/sigma(e+e- -> q-qbar ) is measured for light quarks using event samples collected with the OPAL detector at LEP at centre-of-mass energies between 189 and 209 GeV. The analysis uses high momentum charged pions, charged and neutral kaons, protons and Lambda baryons to identify the different light flavour quark events on a statistical basis. The probabilities for the different particle types to originate from particular primary quarks are determined directly from high statistics data taken at the Z peak, thus making possible a hadronisation model-independent measurement.