A wind turbine blade comprising a lightning protection system, which is at least partly disposed in an inboard portion of the blade. The lightning protection system comprises a down conductor cable having root and tip portions having insulation with different electrical breakdown voltages. The lightning protection system may comprise a down conductor cable portion and a supporting component to hold the cable portion in free space in a position near or on a camber line of the blade aerofoil section, so that the cable portion is spaced apart from at least one electrically conductive structural component; and/or a plurality of inboard down conductor cables and a diverging electrical junction.