Electrosurgical instrument

An electrosurgical instrument is provided for the treatment of tissue, the instrument 1 comprising a handle 2, an instrument shaft 5 extending from the handle and an electrode assembly 6 at the distal end of the shaft. The electrode assembly comprises a tissue treatment electrode 10 and a return electrode 12 that is electrically insulated from the tissue treatment electrode by means of an insulation member 13. The tissue treatment electrode 10 has an exposed surface for treating tissue, where the return electrode 12 has a fluid contact surface that in use define a conductive fluid path that completes an electrical circuit between the electrodes 10&12. The instrument shaft 5 provides a conductive pathway for one of the electrodes and is subjected to a surface treatment so that its surface 7 has been altered whilst maintaining its electrical conductivity. The surface of the instrument shaft 5 may be: oxidised, coloured or matt finished by the surface treatment. The surface treatment may be selected from a list of treatments including phosphate conversion coating, zinc or manganese phosphating, black oxide conversion coating, chrome or nickel plating, or ferritic itrocarburising. The surface treatment may comprise depositing a coating on the instrument shaft 5.