The magnitude of the CKM matrix element $V_{\rm ub}$ is determined by 
measuring the inclusive charmless semileptonic branching fraction of
beauty hadrons at OPAL based on $\rm b\rightarrow X_u\ell\nu$ event
topology and kinematics. This analysis uses OPAL data collected between
1991 and 1995, which correspond to about four million hadronic Z decays.
We measure $\rm Br(b\rightarrow X_u\ell\nu)$ to be 
$(1.63\pm 0.53^{+0.55}_{-0.62})\times 10^{-3}$. The first uncertainty is
the statistical error and the second is the systematic error. From this
analysis, $|V_{\rm ub}|$ is determined to be:
$$
\rm |V_{ub}|=(4.00\pm 0.65 (stat) ^{+0.67}_{-0.76} (sys) \pm 0.19 (HQE))
\times 10^{-3} .
$$
The last error represents the theortical uncertainties related to the 
extraction of $\rm |V_{ub}|$ from $\rm Br(b\rightarrow X_u\ell\nu)$
using the Heavy Quark Expansion.