Magnetising assembly

A magnetiser 20, suitable for an in-line pipe inspection tool, comprises a ferromagnetic base member 21, a pair of driving magnets 22 mounted at spatially separate locations on the base member 21 and where the polarisation direction 31, 32 of the drive magnets 22 are opposite to one another and are direct towards or away from the base member 21, respectively. The magnetiser 20 further includes a flux enhancing magnet 27 which is mounted on the base member 21, adjacent to one or both of the drive magnets 22, and arranged with its polarisation 33 substantially aligned with the flux path passing through the base member 21 and extending between the drive magnets 22. The flux enhancing magnet 27 is coupled to the drive magnets 22 such that the external magnetic field generated by the magnetiser 20 assembly is enhanced. The assembly 20 may include flux couplers 23 and a plurality of flux enhancing magnets. The magnets 22, 27 and base member 21 may be shaped to further enhance the magnetic field generated.