Witten's twistor string theory description of N=4 super Yang-Mills has led to much progress in perturbative Yang-Mills theory this year, with accumulating evidence for the localisation of scattering amplitudes in twistor space in various Yang-Mills theories. This talk will focus on the MHV diagram approach, which builds in localisation, and will describe work done at Queen Mary which shows how to define MHV diagrams at loop level. This has been successfully applied to give the general one-loop MHV amplitudes in N=4 and N=1 super Yang-Mills.