Just not true Jules. The Mayor of London was given a direct mandate for policing in London in 2011, as part of the Police and Social Responsibility Act. As such, the Mayor is responsible for setting the strategic direction of policing in London through the Police and Crime Plan. If there are any problems with policing in London then they rest entirely at the Mayor's doorstep. It's one of the only things he does actually have responsibility for (the other being TfL - another gopping failure).