Abstract: A wind turbine blade is described having a de-icing system which is arranged to heat at least a portion of the leading edge of the wind turbine blade, to prevent the formation of ice on the blade, or to remove any existing surface ice. The de-icing system comprises insulated flow channels which are arranged to circulate a heated fluid from a heating element to the tip end of the blade, and to de-ice the blade leading edge starting from the tip end towards the root end of the blade. The de-icing system is arranged to operate in the outboard portion of the blade, where the de-icing effect provides the most benefits to turbine operation. Further features of the de-icing system include an improved mounting arrangement of the de-icing system, an improved tip end configuration of the de-icing system, and providing portions of the de-icing system as double-walled inflatable insulating tubes.