A method of making a wind turbine blade having a main blade section and a tip section connected together, the method comprising: providing a main blade mould assembly comprising first and second female main mould halves (30a, 30b) shaped to form first and second half shells (42a, 42b) of the main blade section respectively, each main mould half having an inboard end (32a, 32b) shaped to define a radially inboard portion of the main blade section and an outboard end (34a, 34b) shaped to define a radially outboard portion of the main blade section, the main blade mould assembly having an open position in which the main mould halves are spaced apart, and a closed position in which the main mould halves are brought together; forming a first half shell of the main blade section in the first main mould half and forming a second half shell of the main blade section in the second main mould half with the main blade mould assembly in the open position; selecting a tip section from a plurality of tip sections of different lengths according to a total length requirement for the wind turbine blade; arranging the tip section adjacent to the outboard end of the first main mould half such that an inboard end of the tip section and an outboard end of the first half shell overlap; closing the main mould assembly such that the first and second half shells (42a, 42b) are brought together and such that the inboard end of the tip section and an outboard end of the second half shell overlap; and bonding the first and second half shells together (42a, 42b) and simultaneously bonding the inboard end of the tip section to the outboard ends of the first and second half shells with the main mould assembly in the closed position. providing a main blade mould assembly comprising first and second female main mould halves (30a, 30b) shaped to form first and second half shells (42a, 42b) of the main blade section respectively, each main mould half having an inboard end (32a, 32b) shaped to define a radially inboard portion of the main blade section and an outboard end (34a, 34b) shaped to define a radially outboard portion of the main blade section, the main blade mould assembly having an open position in which the main mould halves are spaced apart, and a closed position in which the main mould halves are brought together; forming a first half shell of the main blade section in the first main mould half and forming a second half shell of the main blade section in the second main mould half with the main blade mould assembly in the open position; selecting a tip section from a plurality of tip sections of different lengths according to a total length requirement for the wind turbine blade; arranging the tip section adjacent to the outboard end of the first main mould half such that an inboard end of the tip section and an outboard end of the first half shell overlap; closing the main mould assembly such that the first and second half shells (42a, 42b) are brought together and such that the inboard end of the tip section and an outboard end of the second half shell overlap; and bonding the first and second half shells together (42a, 42b) and simultaneously bonding the inboard end of the tip section to the outboard ends of the first and second half shells with the main mould assembly in the closed position.