  We present some preliminary results for $B_K$ at $\beta=6.0$, using the
twisted mass QCD formalism for the computation of bare matrix elements of the
$\Delta S=2$ operator. The main advantage of the method is that mixing with
other $d=6$ operators under renormalisation is avoided. Moreover the operator
renormalisation is performed in the Schr\"odinger functional (SF) framework,
using earlier results of our collaboration for the corresponding step scaling
function.
