A method for the manufacture of a component having an internal cavity is described. The method comprises; defining an external geometry of the component, defining a core geometry of the component; and using an additive layer manufacturing (ALM) method, building the component from a plurality of layers laid on a first plane. The core geometry is advantageously designed to suit manufacture of the component using an ALM method which involves local melting of powder in a powder bed to form the layers, permitting easy removal of excess powder from the internal cavity.