A surgical instrument comprising: a handle; and an elongated shaft assembly extending distally from the handle, wherein the elongated shaft assembly includes an articulable portion with an articulation direction, wherein the elongated shaft assembly comprises: a first tubular member including a first flexible portion including a first plurality of slots and at least a first spine extending along a length of the first flexible portion; whereby the elongated shaft assembly further comprises: a second tubular member, characterised in that the second tubular member includes a second flexible portion including a second plurality of slots and at least a second spine extending along a length of the second flexible portion, wherein the first tubular member and the second tubular member are axially fixed relative to one another at a position distal from the first flexible portion and the second flexible portion; and in that the elongated shaft assembly further comprises a third tubular member including a third flexible portion with a third plurality of slots, a third spine, and a fourth spine extending along a length of the third flexible portion, wherein the first tubular member, the second tubular member, and the third tubular member are coaxially located, and wherein the third tubular member is rotatable relative to the first tubular member and/or the second tubular member. a handle; and an elongated shaft assembly extending distally from the handle, wherein the elongated shaft assembly includes an articulable portion with an articulation direction, wherein the elongated shaft assembly comprises: a first tubular member including a first flexible portion including a first plurality of slots and at least a first spine extending along a length of the first flexible portion; whereby the elongated shaft assembly further comprises: a second tubular member, characterised in that the second tubular member includes a second flexible portion including a second plurality of slots and at least a second spine extending along a length of the second flexible portion, wherein the first tubular member and the second tubular member are axially fixed relative to one another at a position distal from the first flexible portion and the second flexible portion; and in that the elongated shaft assembly further comprises a third tubular member including a third flexible portion with a third plurality of slots, a third spine, and a fourth spine extending along a length of the third flexible portion, wherein the first tubular member, the second tubular member, and the third tubular member are coaxially located, and wherein the third tubular member is rotatable relative to the first tubular member and/or the second tubular member. a first tubular member including a first flexible portion including a first plurality of slots and at least a first spine extending along a length of the first flexible portion; whereby the elongated shaft assembly further comprises: a second tubular member, characterised in that the second tubular member includes a second flexible portion including a second plurality of slots and at least a second spine extending along a length of the second flexible portion, wherein the first tubular member and the second tubular member are axially fixed relative to one another at a position distal from the first flexible portion and the second flexible portion; and in that the elongated shaft assembly further comprises a third tubular member including a third flexible portion with a third plurality of slots, a third spine, and a fourth spine extending along a length of the third flexible portion, wherein the first tubular member, the second tubular member, and the third tubular member are coaxially located, and wherein the third tubular member is rotatable relative to the first tubular member and/or the second tubular member.