A method of inspecting a turbomachine, the turbomachine comprising a rotor having a plurality of stages (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades and a casing (60,62) surrounding the rotor and at least one stage (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades, each rotor blade comprising a platform portion and an aerofoil portion, the aerofoil portion having a leading edge, a trailing edge, a concave surface, a convex surface and a tip, the method comprising the steps of a) providing a plurality of boroscopes, b) inserting each boroscope through a respective one of a plurality of apertures (66, 68) in a casing (60,62) of the turbomachine, at least one of the apertures (66,68) in the casing (60,62) being upstream of the rotor blades, at least one of the apertures (66,68) in the casing (60,62) being downstream of the rotor blades, placing a boroscope upstream of each one of the plurality of stages (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades and placing a boroscope downstream of each one of the plurality of stages (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades, c) rotating the rotor of the turbomachine, d) providing reference measurements of the rotor blades and/or reference measurements between the rotor blades and the boroscopes, providing reference measurements of the rotor blades of each of the stages (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades and/or reference measurements between the rotor blades of each of the stages (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades and the corresponding boroscopes, e) viewing the leading edge and at least a portion of the concave surface or viewing the leading edge and at least a portion of the convex surface of each of the rotor blades of the turbomachine as the rotor is rotated using the boroscope in the at least one of the apertures (66,68) in the casing (60,62) upstream of the rotor blades and supplying the image of each of the rotor blades to the processor, f) viewing the trailing edge and at least a portion of the convex surface or viewing the trailing edge and at least a portion of the concave surface of each of the rotor blades of the turbomachine as the rotor is rotated using the boroscope in the at least one of the apertures (66,68) in the casing (60,62) downstream of the rotor blades and supplying the image of each of the rotor blades to the processor, and g) analysing the images of the rotor blades and using the reference measurements of the rotor blades and/or reference measurements between the rotor blades and the boroscopes to determine the position and size of any defect on any of the rotor blades, analysing the images of the rotor blades of each of the stages (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades and using the reference measurements of the rotor blades for each stage (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades and/or reference measurements between the rotor blades of each stage (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades and the corresponding boroscopes to determine the position and size of any defect on any of the rotor blades. a) providing a plurality of boroscopes, b) inserting each boroscope through a respective one of a plurality of apertures (66, 68) in a casing (60,62) of the turbomachine, at least one of the apertures (66,68) in the casing (60,62) being upstream of the rotor blades, at least one of the apertures (66,68) in the casing (60,62) being downstream of the rotor blades, placing a boroscope upstream of each one of the plurality of stages (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades and placing a boroscope downstream of each one of the plurality of stages (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades, c) rotating the rotor of the turbomachine, d) providing reference measurements of the rotor blades and/or reference measurements between the rotor blades and the boroscopes, providing reference measurements of the rotor blades of each of the stages (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades and/or reference measurements between the rotor blades of each of the stages (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades and the corresponding boroscopes, e) viewing the leading edge and at least a portion of the concave surface or viewing the leading edge and at least a portion of the convex surface of each of the rotor blades of the turbomachine as the rotor is rotated using the boroscope in the at least one of the apertures (66,68) in the casing (60,62) upstream of the rotor blades and supplying the image of each of the rotor blades to the processor, f) viewing the trailing edge and at least a portion of the convex surface or viewing the trailing edge and at least a portion of the concave surface of each of the rotor blades of the turbomachine as the rotor is rotated using the boroscope in the at least one of the apertures (66,68) in the casing (60,62) downstream of the rotor blades and supplying the image of each of the rotor blades to the processor, and g) analysing the images of the rotor blades and using the reference measurements of the rotor blades and/or reference measurements between the rotor blades and the boroscopes to determine the position and size of any defect on any of the rotor blades, analysing the images of the rotor blades of each of the stages (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades and using the reference measurements of the rotor blades for each stage (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades and/or reference measurements between the rotor blades of each stage (51A, 51B, 51C, 51D, 51E, 51F) of rotor blades and the corresponding boroscopes to determine the position and size of any defect on any of the rotor blades.