  Hadronic final states with a hard isolated photon are studied using data
taken at centre-of-mass energies around the mass of the Z0 boson with the OPAL
detector at LEP. The strong coupling alpha S is extracted by comparing data and
QCD predictions for event shape observables at average reduced centre-of-mass
energies ranging from 24 GeV to 78 GeV, and the energy dependence of alpha S is
studied. Our results are consistent with the running of alpha S as predicted by
QCD and show that within the uncertainties of our analysis event shapes in
hadronic Z0 decays with hard and isolated photon radiation can be described by
QCD at reduced centre-of-mass energies. Combining all values from different
event shape observables and energies gives alpha S (Mz)=0.1182 pm 0.0015(stat.)
pm 0.0101(syst.).
