Powering an electrocautery surgical instrument

An instrument comprising a shaft 402 connected by an articulation 403, which may be a pulley arrangement, to an electrocautery effector 401 powered by an electrocautery element E1 bonded to a driving element in the shaft. The electrocautery element may be a wire. The articulation comprises a first joint 404 with a pair of driving elements A1-2, which may be cables, for rotating the effector about first axis 405 transverse to the longitudinal axis of the shaft, and a second joint 407 with driving elements B1-2 for rotating the effector about second axis 408 transverse to the first. The wire moves around the first axis and wraps at least one full revolution around the second axis. The pulley arrangement may include further pulleys between the first axis and the second axis or shaft. The path of the wire between the shaft and second joint may symmetrically oppose a driving element.