A robotic surgical instrument comprising: a shaft； an articulation at a distal end of the shaft for articulating an end effector, the articulation driveable by pairs of driving elements； and an instrument interface at a proximal end of the shaft, the instrument interface comprising an internal portion which is within the projected profile of the shaft and an external portion which is outside of the projected profile of the shaft, the instrument interface comprising instrument interface elements for driving pairs of driving elements, wherein a first instrument interface element engages a first pair of driving elements in the internal portion.
