A clamping mechanism comprising a first part provided with a first magnetic component, a second part, and a third part provided with a second magnetic component and being coupled to the second part. The mechanism is such that, bringing the first and second parts together along an axis causes rotational alignment and relative radial movement of the first and second magnetic components to effect axial clamping of the first part to the second part, and wherein relative rotation of the first and third parts to misalign the first and second magnetic components reverses this radial movement and effects unclamping of the first and second parts.