A method of manufacturing a wind turbine blade comprising a fairing supported by a spar extending from a root to a tip, wherein the spar comprises a spar section of a main part of the fairing and a tip spar section of a wind turbine blade tip section, wherein the spar section of the main part is connected to the tip spar section, the method comprising moulding the wind turbine blade tip section, the tip section being at least 5 metres long, the method of moulding the wind turbine blade tip section comprising: laying up first composite material into a first mould half, laying up second composite material into a second mould half, providing at least one of the mould halves with an extension for supporting overlap material, wherein the extension comprises an internal profile with a stepped configuration to define a progressively stepped down shape of the overlap material; laying up overlap material across the extension, the overlap material being continuous with the material in the rest of the mould half, supporting the overlap material with a pressure bag, removing the extension before the step of bringing the mould halves together so that the overlap material fuses with the material of the material in the other mould half during the curing process, and bringing the mould halves together so that the first and second composite materials overlap where the first and second mould halves meet; and curing the first and second composite materials simultaneously so that the matrices of the first and second composite materials fuse in the regions where the composite materials overlap such that seamless joints are formed in the regions where the composite materials overlap; the main part of the fairing extending from the root to the wind turbine blade tip section, the method of manufacturing the wind turbine blade further comprising connecting the spar section of the main part of the fairing with the tip spar section, wherein the method of moulding the wind turbine blade tip section further comprises co-moulding a first spar cap in the first mould half and co-moulding a second spar cap in the second mould half and co-moulding a shear web between the spar caps (17,18). laying up first composite material into a first mould half, laying up second composite material into a second mould half, providing at least one of the mould halves with an extension for supporting overlap material, wherein the extension comprises an internal profile with a stepped configuration to define a progressively stepped down shape of the overlap material; laying up overlap material across the extension, the overlap material being continuous with the material in the rest of the mould half, supporting the overlap material with a pressure bag, removing the extension before the step of bringing the mould halves together so that the overlap material fuses with the material of the material in the other mould half during the curing process, and bringing the mould halves together so that the first and second composite materials overlap where the first and second mould halves meet; and curing the first and second composite materials simultaneously so that the matrices of the first and second composite materials fuse in the regions where the composite materials overlap such that seamless joints are formed in the regions where the composite materials overlap; the main part of the fairing extending from the root to the wind turbine blade tip section, the method of manufacturing the wind turbine blade further comprising connecting the spar section of the main part of the fairing with the tip spar section, wherein the method of moulding the wind turbine blade tip section further comprises co-moulding a first spar cap in the first mould half and co-moulding a second spar cap in the second mould half and co-moulding a shear web between the spar caps (17,18).