The inclusive branching ratio for the process b --> tau (-)(v) over bar X-t
au has been measured using hadronic Z decays collected by the OPAL experime
nt at LEP in the years 1992-2000. The result is: BR(b --> tau (-)(v) over b
ar X-tau) = (2.78 +/- 0.18 +/- 0.51)%. This measurement is consistent with
the Standard Model expectation and puts a constraint of tan beta /M-H(+/-)
< 0.53 GeV-1 at the 95% confidence level on Type II Two Higgs Doublet Model
s. (C) 2001 Elsevier Science B.V. All rights reserved.