A wind turbine blade comprising an aerodynamic fairing supported along at least a portion of its axial length by a spar (12). The spar comprises at least two spar segments (12) joined end-to-end at an interface (9), each spar segment comprising a shear web (3) with a spar cap (4) on each side. The outer face (6) of each spar cap tapers inwardly towards the interface such that its depth is reduced towards the interface creating a recess on each side of the interface formed by the tapered faces of adjacent spar caps. A respective connection piece (8) is sized to fit into each recess. Each connection piece (8) is sized to fit into each recess. Each connection piece (8) being fixed to the tapered faces of adjacent spar caps to form a double scarf joint.
