  We present the results of a precision computation of B_K with Wilson
fermions. Simulations are performed at different lattice spacings, enabling
continuum limit extrapolations. Two different twisted mass QCD (tmQCD)
regularisations are considered for the computation of bare matrix elements. In
both cases the relevant four-fermion operator renormalises multiplicatively. In
one regularisation it is possible to perform the computation directly at the
physical kaon mass value, thus avoiding extrapolations in the mass.
Nonperturbative renormalisation is carried out using available Schroedinger
Functional results.
