The high luminosity delivered by LEP after the increase of the e⁺e^- collision energy means that LEP2 is now providing substantial data samples with which to make complementary tests of the Standard Model to those of LEP1. Based on the analysis of about 710 pb^-1 of data recorded at centre-of-mass energies between 172 GeV and 210 GeV with the OPAL detector at LEP, several measurements and comparisons with the Standard Model expectations are described. In particular, results on the cross-section for WW production and the partial decay width R_c^W = Gamma(W to cX)/\Gamma(W to hadrons). These results are used to determine the CKM matrix element |V_cs| and to review the existing constraints on |V_cs| from D semileptonic decays, neutrino beam experiments, and the LEP Collaborations. Emphasis is also given on the search for flavour-changing-neutral-current (FCNC) in single top production at LEP2 energies and on the determination of limits for new physics. Future prospects for more precise experimental information on |V_cs| and FCNC will be discussed.

Monday, January 29th 2001, 15:30
Ernest Rutherford Physics Building, room 305