  We compute the leading colour contributions to five-gluon scattering at two
loops in massless QCD. The integrands of all independent helicity amplitudes
are evaluated using d-dimensional generalised unitarity cuts and finite field
reconstruction techniques. Numerical evaluation of the integral basis is
performed with sector decomposition methods to obtain the first benchmark
results for all helicity configurations of a 2 to 3 scattering process in QCD.
