An electrosurgical instrument includes an instrument shaft having a longitudinal axis, and an electrode assembly at one end of the shaft, the electrode assembly including first, second and third electrodes which are electrically insulated one from another by means of one or more insulation members. The instrument further includes first and second connections by which RF energy can be supplied to the instrument from an electrosurgical generator. The first electrode is movable longitudinally between an advanced position in which it extends from the instrument shaft and a retracted position in which it is less advanced with respect to the instrument shaft. When the first electrode is in its advanced position, the first and second connections are in electrical communication with the first and second electrodes. When moved to its retracted position, the first and second connections are caused to be in electrical communication with the second and third electrodes.