The mass of the W boson has been measured by the LEP collaborations from the data recorded during the LEP2 programme at e+ e- centre of mass energies from 161 to 209 GeV, giving the result : mw = 80.450 +/- 0.039 GeV/c^2. This paper discusses the measurements of the W Mass from direct reconstruction of the invariant mass of the WW decay products, particular emphasis is placed on the evaluation of systematic errors. Results on the direct measurement of the W width are also presented.
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