  We present results for the semi-leptonic and leptonic decays of B mesons.
These non-perturbative matrix elements are important for constraining the CKM
matrix. Results are presented for the pseudoscalar and vector decay constants,
as well as flavour breaking ratios and heavy quark symmetry relations. We
consider the chiral and momentum dependence of the semi-leptonic form factors
of the decay B-> pi l nu and the soft pion relation (SPR) on the lattice. These
calculations were performed in the quenched approximation at two values of the
coupling with non-perturbatively order a improved action and currents.
