An electrosurgical cutting tool having: a first blade and a second blade, joined at a pivot point, with the first blade comprising a planar body made of a first dielectric material separating a first conductive element on a first surface thereof from a second conductive element on a second surface thereof, the second surface facing in the opposite direction to the first surface; actuation means for causing relative rotation between the first and second blades about the pivot point to cause a gap between the first blade and second blade to change between an open position and a closed position, the relative rotation being substantially in the plane of the blades; a coaxial transmission line for delivering RF energy and microwave energy to the first blade, the coaxial transmission line having an inner conductor and an outer conductor separated by a second dielectric material, wherein: the inner conductor and the outer conductor are each connected to one of the first conductive element and the second conductive element of the first blade; the first conductive element and the second conductive element of the first blade are able to act as active and return electrodes for sustaining an RF electric field therebetween, the RF electric field corresponding to RF energy delivered to the first blade by the coaxial transmission line; the first conductive element and the second conductive element of the first blade are able also to act as an antenna structure for radiating a microwave electromagnetic field corresponding to microwave energy delivered to the first blade by the coaxial transmission line, characterised in that the blades are mounted in a clevis structure which is located at the distal end of the cutting tool, the clevis structure comprising a base for attaching to the coaxial transmission line, and a housing that defines a longitudinal recess for receiving the first blade and second blade, wherein the clevis structure comprises an axle that traverses the recess, and wherein the first blade and the second blade are rotatably mounted on the axle, wherein the electrical connections between the inner conductor and the outer conductor of the coaxial transmission line and the first conductive element and second conductive element on the first blade are made via a conductive sleeve on the axle. a first blade and a second blade, joined at a pivot point, with the first blade comprising a planar body made of a first dielectric material separating a first conductive element on a first surface thereof from a second conductive element on a second surface thereof, the second surface facing in the opposite direction to the first surface; actuation means for causing relative rotation between the first and second blades about the pivot point to cause a gap between the first blade and second blade to change between an open position and a closed position, the relative rotation being substantially in the plane of the blades; a coaxial transmission line for delivering RF energy and microwave energy to the first blade, the coaxial transmission line having an inner conductor and an outer conductor separated by a second dielectric material, wherein: the inner conductor and the outer conductor are each connected to one of the first conductive element and the second conductive element of the first blade; the first conductive element and the second conductive element of the first blade are able to act as active and return electrodes for sustaining an RF electric field therebetween, the RF electric field corresponding to RF energy delivered to the first blade by the coaxial transmission line; the first conductive element and the second conductive element of the first blade are able also to act as an antenna structure for radiating a microwave electromagnetic field corresponding to microwave energy delivered to the first blade by the coaxial transmission line, characterised in that the blades are mounted in a clevis structure which is located at the distal end of the cutting tool, the clevis structure comprising a base for attaching to the coaxial transmission line, and a housing that defines a longitudinal recess for receiving the first blade and second blade, the inner conductor and the outer conductor are each connected to one of the first conductive element and the second conductive element of the first blade; the first conductive element and the second conductive element of the first blade are able to act as active and return electrodes for sustaining an RF electric field therebetween, the RF electric field corresponding to RF energy delivered to the first blade by the coaxial transmission line; the first conductive element and the second conductive element of the first blade are able also to act as an antenna structure for radiating a microwave electromagnetic field corresponding to microwave energy delivered to the first blade by the coaxial transmission line, characterised in that the blades are mounted in a clevis structure which is located at the distal end of the cutting tool, the clevis structure comprising a base for attaching to the coaxial transmission line, and a housing that defines a longitudinal recess for receiving the first blade and second blade, wherein the clevis structure comprises an axle that traverses the recess, and wherein the first blade and the second blade are rotatably mounted on the axle, wherein the electrical connections between the inner conductor and the outer conductor of the coaxial transmission line and the first conductive element and second conductive element on the first blade are made via a conductive sleeve on the axle.