A surgical robot comprising: a base ; and an arm extending from the base and terminating at its distal end in a wrist having thereon an attachment for a surgical instrument; and a surgical instrument attached to the attachment; wherein: the arm is articulated by a series of revolute joints along its length, the arm joints comprising, in order running from the base: i. a first joint having a first axis ; ii. a second joint having a second axis transverse to the first axis; iii. a third joint having a third axis transverse to the second axis; and iv. a fourth joint having a fourth axis transverse to the third axis; and the wrist is articulated by a second series of revolute joints along its length such that in a configuration in which the distal end of the arm is collinear with the attachment for the surgical instrument, the joints of the wrist comprise, in order running towards the attachment: v. a fifth joint having a fifth axis ; vi. a sixth joint having a sixth axis transverse to the fifth axis; vii. a seventh joint having a seventh axis that intersects the sixth axis and is transverse to both the fifth and sixth axes; and viii. an eighth joint having an eighth axis parallel to the fifth axis, wherein the surgical instrument has an axis of elongation aligned with the eighth axis. a base ; and an arm extending from the base and terminating at its distal end in a wrist having thereon an attachment for a surgical instrument; and a surgical instrument attached to the attachment; the arm is articulated by a series of revolute joints along its length, the arm joints comprising, in order running from the base: i. a first joint having a first axis ; ii. a second joint having a second axis transverse to the first axis; iii. a third joint having a third axis transverse to the second axis; and iv. a fourth joint having a fourth axis transverse to the third axis; and i. a first joint having a first axis ; ii. a second joint having a second axis transverse to the first axis; iii. a third joint having a third axis transverse to the second axis; and iv. a fourth joint having a fourth axis transverse to the third axis; and the wrist is articulated by a second series of revolute joints along its length such that in a configuration in which the distal end of the arm is collinear with the attachment for the surgical instrument, the joints of the wrist comprise, in order running towards the attachment: v. a fifth joint having a fifth axis ; vi. a sixth joint having a sixth axis transverse to the fifth axis; vii. a seventh joint having a seventh axis that intersects the sixth axis and is transverse to both the fifth and sixth axes; and viii. an eighth joint having an eighth axis parallel to the fifth axis, wherein the surgical instrument has an axis of elongation aligned with the eighth axis. v. a fifth joint having a fifth axis ; vi. a sixth joint having a sixth axis transverse to the fifth axis; vii. a seventh joint having a seventh axis that intersects the sixth axis and is transverse to both the fifth and sixth axes; and viii. an eighth joint having an eighth axis parallel to the fifth axis, wherein the surgical instrument has an axis of elongation aligned with the eighth axis. <EOS>