In a first aspect of the invention there is provided a method of making a wind turbine blade. The method comprises providing a blade shell mould, providing a plurality of 5 substantially planar strips of reinforcing material, and arranging the plurality of strips in the mould in a first stack to form at least part of a first spar cap. The method further comprises providing a retaining clip having a substantially planar body and upper and lower flanges projecting transversely to the planar body, wherein the flanges and the body together define a first receiving region on a first side of the retaining clip, and the 10 method further comprises arranging the retaining clip on a side of the first stack such that the strips in the first stack are received in the first receiving region.