A method of forming a protective sheath for an aerofoil component includes: providing a first sheath portion and a second sheath portion, the first sheath portion and the second sheath portion each comprising an inner surface, an outer surface and an end surface between the inner and outer surfaces and having a sacrificial flange at its distal end; positioning the first sheath portion and second sheath portion so that the inner surface of the first sheath portion abuts against the inner surface of the second sheath portion with the end surfaces of the first and second sheath portions aligned to form a mating edge; and joining the first sheath portion to the second sheath portion by welding along the mating edge, wherein the sacrificial flanges are completely consumed and a curved outer profile is formed.