Powering a bipolar electrocautery surgical instrument

A robotic surgical instrument comprising a shaft, an electrocautery end effector powered by a first electrocautery element and a second electrocautery element,and an articulation. The articulation connects the electrocautery end effector to the shaft,and comprises a first joint driveable by a first pair of driving elements, the first joint permitting the electrocautery end effector to rotate about a first axis transverse to a longitudinal axis of the shaft. The first joint comprises a pulley arrangement around which the first pair of driving elements and the first and second electrocautery elements are constrained to move, the first and second electrocautery elements having symmetrically opposing paths around the pulley arrangement. The first and second electrocautery elements are distinct from the first pair of driving elements.