A power axle wrist for a surgical tool that couples an end effector to an elongate shaft of the surgical tool, the power axle wrist comprising: a distal clevis having a first axle where the end effector is rotatably mounted to the distal clevis, the end effector being articulable about a first pivot axis (P 1 ) extending through the first axle; a proximal clevis configured to be coupled to a distal end of the elongate shaft and having a second axle where the distal clevis is rotatably mounted to the proximal clevis; a power axle cable mounted to the distal clevis such that movement of the power axle cable correspondingly pivots the end effector about a second pivot axis (P 2 ) extending through the second axle and perpendicular to the first pivot axis; a first plurality of pulleys mounted to the second axle; and a second plurality of pulleys mounted to a third axle coupled to the proximal clevis and located proximal to the second axle; wherein the first and second plurality of pulleys are configured to cooperatively redirect a plurality of drive cables (308a-d) through an S-shaped pathway while the power axle cable is routed directly to the distal clevis; characterised in that an outer diameter of each pulley of the first and second pluralities of pulleys is the same, but the second axle is larger than the third axle and an inner diameter of each pulley of the second plurality of pulleys is smaller than an inner diameter of each pulley of the first plurality of pulleys, and wherein the smaller inner diameter of each second plurality of pulleys equates to less bend angle applied to the drive cables as they are routed through the S-shaped pathway. a distal clevis having a first axle where the end effector is rotatably mounted to the distal clevis, the end effector being articulable about a first pivot axis (P 1 ) extending through the first axle; a proximal clevis configured to be coupled to a distal end of the elongate shaft and having a second axle where the distal clevis is rotatably mounted to the proximal clevis; a power axle cable mounted to the distal clevis such that movement of the power axle cable correspondingly pivots the end effector about a second pivot axis (P 2 ) extending through the second axle and perpendicular to the first pivot axis; a first plurality of pulleys mounted to the second axle; and a second plurality of pulleys mounted to a third axle coupled to the proximal clevis and located proximal to the second axle; wherein the first and second plurality of pulleys are configured to cooperatively redirect a plurality of drive cables (308a-d) through an S-shaped pathway while the power axle cable is routed directly to the distal clevis; characterised in that an outer diameter of each pulley of the first and second pluralities of pulleys is the same, but the second axle is larger than the third axle and an inner diameter of each pulley of the second plurality of pulleys is smaller than an inner diameter of each pulley of the first plurality of pulleys, and wherein the smaller inner diameter of each second plurality of pulleys equates to less bend angle applied to the drive cables as they are routed through the S-shaped pathway. <EOS>