A method of manufacturing a wind turbine blade shell part is described. Fibre mats and a root end insert are laid up in a mould part in a layup procedure by use of an automated layup system. The fibre mats are laid up by use of a buffer so that the fibre mats may continuously be laid up on the mould surface, also during a cutting procedure. The root end insert is prepared in advance and mounted on a mounting plate. The root end insert is lowered onto the mould by use of the mounting plate and a lowering mechanism. After the wind turbine blade shell has been moulded, the mounting plate is removed.