There is disclosed a clamp, a self-advancing climbing device including two such clamps, and a method of coupling such a clamp to a tubular. In one embodiment of the invention, there is disclosed a clamp (1) for a tubular, in particular a thin-walled tubular such as the tower (3) of a wind-turbine. The clamp (1) comprises at least one clamp member in the form of a friction pad (9) adapted to grip the tower (3), and at least one flexible elongate energising element in the form of a tendon (16) adapted to exert a force on the friction pad (9) to urge the pad (9) to grip the tower (3), whereby the pad (9) and the tendon (16) are adapted to exert a substantially uniform radial clamp load on the tower (3).