A mould for moulding a wind turbine blade or an elongate structural part thereof, the mould comprising a plurality of longitudinal elongate mould sections adapted to be fitted together in an end-to-end relationship to form a unitary mould, each mould section having a central mould portion between opposite end portions, each mould section being composed of a fibre reinforced resin matrix composite material, at least one end portion of each mould section forming an integral flange oriented substantially orthogonally downwardly with respect to an upper surface of the mould section, and the upper surface including a moulding surface and a recess located between the flange and the moulding surface, the recess extending across a transverse width of the mould section whereby when the flanges of adjacent mould sections are fitted together in an abutting relationship, the adjacent recesses form a combined recess separating the moulding surfaces of the adjacent mould sections.