A method of making a wind turbine blade is described. The blade comprises an outer shell having a laminate structure. The method comprises providing a blade mould (82) defining a shape of at least part of the outer shell of the blade. The mould extends in a spanwise direction between a root end (94) and a tip end (96), and extends in a chordwise direction between a leading edge (90) and a trailing edge (92). The method further includes providing a plurality of dry plies (66) comprising dry structural fibrous material and a plurality of prepreg (68) plies comprising structural fibrous material impregnated with resin. The plurality of dry plies and the plurality of prepreg plies are arranged in the mould to form a plurality of layers of the laminate structure of the outer shell of the blade. The plies are arranged in the mould such that the dry plies are interleaved with the prepreg plies to form a hybrid shell structure in which the plies are arranged in a staggered relationship such that corresponding edges of the dry plies are offset from one another in the spanwise and/or chordwise direction of the mould and/or corresponding edges of the prepreg plies are offset from one another in the spanwise and/or chordwise direction of the mould.