A robotic surgical instrument comprising: a shaft; an electrocautery end effector powered by an electrocautery element, wherein the electrocautery element is a cable; and an articulation connecting the electrocautery end effector to the shaft, the articulation comprising: a first body part and a second body part; a first joint driveable by a first pair of driving elements (A1, A2), the first joint permitting the electrocautery end effector to rotate about a first axis transverse to a longitudinal axis of the shaft and permitting the second body part to rotate relative to the shaft about the first axis, a second distal joint driveable by a second pair of driving elements (B1, B2), the second joint permitting the electrocautery end effector to rotate about a second axis transverse to the first axis and permitting the electrocautery end effector to rotate relative to the second body part about the second axis; and a pulley arrangement around which the second pair of driving elements and the electrocautery element are constrained to move; wherein the electrocautery element is constrained to move around the first axis and constrained to wrap at least one full revolution around the second axis; and characterised in that in the straight configuration of the instrument in which the electrocautery end effector is aligned with the shaft, the path of the electrocautery element around the pulley arrangement is rotationally symmetrical about the longitudinal axis of the shaft to the path of the first one of the second pair of driving elements around the pulley arrangement, and wherein the electrocautery element is attached to a second one of the second pair of driving elements in the shaft a shaft; an electrocautery end effector powered by an electrocautery element, wherein the electrocautery element is a cable; and an articulation connecting the electrocautery end effector to the shaft, the articulation comprising: a first body part and a second body part; a first joint driveable by a first pair of driving elements (A1, A2), the first joint permitting the electrocautery end effector to rotate about a first axis transverse to a longitudinal axis of the shaft and permitting the second body part to rotate relative to the shaft about the first axis, a second distal joint driveable by a second pair of driving elements (B1, B2), the second joint permitting the electrocautery end effector to rotate about a second axis transverse to the first axis and permitting the electrocautery end effector to rotate relative to the second body part about the second axis; and a pulley arrangement around which the second pair of driving elements and the electrocautery element are constrained to move; a first body part and a second body part; a first joint driveable by a first pair of driving elements (A1, A2), the first joint permitting the electrocautery end effector to rotate about a first axis transverse to a longitudinal axis of the shaft and permitting the second body part to rotate relative to the shaft about the first axis, a second distal joint driveable by a second pair of driving elements (B1, B2), the second joint permitting the electrocautery end effector to rotate about a second axis transverse to the first axis and permitting the electrocautery end effector to rotate relative to the second body part about the second axis; and a pulley arrangement around which the second pair of driving elements and the electrocautery element are constrained to move; wherein the electrocautery element is constrained to move around the first axis and constrained to wrap at least one full revolution around the second axis; and characterised in that in the straight configuration of the instrument in which the electrocautery end effector is aligned with the shaft, the path of the electrocautery element around the pulley arrangement is rotationally symmetrical about the longitudinal axis of the shaft to the path of the first one of the second pair of driving elements around the pulley arrangement, and wherein the electrocautery element is attached to a second one of the second pair of driving elements in the shaft