Electrosurgical apparatus for treating biological tissue with radiofrequency energy, the apparatus comprising: a radiofrequency signal generator for generating an RF waveform; a bipolar electrosurgical instrument arranged to deliver the RF waveform from a distal end thereof; a feed structure for conveying the RF waveform to the bipolar electrosurgical instrument along an RF channel; an RF signal detector for sampling current and voltage on the RF channel and generating therefrom a RF detection signal indicative of the current and voltage; and a controller in communication with the RF signal detector to receive the RF detection signal, wherein the controller is arranged to: set a maximum voltage limit for a voltage applied across the bipolar electrosurgical instrument; characterized in that the controller is further arranged to: calculate a tissue resistance based on the RF detection signal, the calculated tissue resistance including a correction for an impedance associated with the RF channel; determine an objective tissue current limit from the calculated tissue resistance and a predetermined power dissipation target; and dynamically adjust a current limit of the RF signal generator based on the determined objective tissue current limit. a radiofrequency signal generator for generating an RF waveform; a bipolar electrosurgical instrument arranged to deliver the RF waveform from a distal end thereof; a feed structure for conveying the RF waveform to the bipolar electrosurgical instrument along an RF channel; an RF signal detector for sampling current and voltage on the RF channel and generating therefrom a RF detection signal indicative of the current and voltage; and a controller in communication with the RF signal detector to receive the RF detection signal, wherein the controller is arranged to: set a maximum voltage limit for a voltage applied across the bipolar electrosurgical instrument; characterized in that the controller is further arranged to: calculate a tissue resistance based on the RF detection signal, the calculated tissue resistance including a correction for an impedance associated with the RF channel; determine an objective tissue current limit from the calculated tissue resistance and a predetermined power dissipation target; and dynamically adjust a current limit of the RF signal generator based on the determined objective tissue current limit. set a maximum voltage limit for a voltage applied across the bipolar electrosurgical instrument; characterized in that the controller is further arranged to: calculate a tissue resistance based on the RF detection signal, the calculated tissue resistance including a correction for an impedance associated with the RF channel; determine an objective tissue current limit from the calculated tissue resistance and a predetermined power dissipation target; and dynamically adjust a current limit of the RF signal generator based on the determined objective tissue current limit. calculate a tissue resistance based on the RF detection signal, the calculated tissue resistance including a correction for an impedance associated with the RF channel; determine an objective tissue current limit from the calculated tissue resistance and a predetermined power dissipation target; and dynamically adjust a current limit of the RF signal generator based on the determined objective tissue current limit.