A fixing assembly for releasably attaching an element to a rotatable ferromagnetic shaft comprising a non-magnetic annular housing (10) comprising at least one substantially diametrically opposed pair of radial bores (12), the bores (12) each housing a magnet (14) with substantially the same dimensions as the bore (12) which is slideable within the bore (12), each magnet (14) being arranged so that its end nearest the axis of the annular housing (10) is the same pole.