A Residual Current Breaker with Overload, RCBO, comprising: at least one phase circuit (20, 21); a neutral circuit; a current sense toroid through which the at least one phase circuit and neutral circuit pass to form a primary winding; contact means to make or break the at least one phase circuit (20,21); a spring loaded actuator lever for operating the contact means via an actuator linkage and actuator mechanism with overload linkage; a magnetic relay with two trigger terminal inputs; a trip linkage slideably engaging the magnetic relay and the actuator mechanism; a secondary winding on said sense toroid connected to said magnetic relay trigger terminal inputs; and when a current imbalance between the at least one phase circuit (20, 21) and neutral circuit exists, current is induced in the secondary winding via the sense toroid sufficient to actuate the magnetic relay to release the elastic potential energy stored in a spring within the magnetic relay to provide the trip linkage with sufficient kinetic energy to trigger the overload linkage of the actuator mechanism and break the contact means, characterised in that the RCBO comprises a reset linkage connected at a proximal end to the actuator lever and at a distal end slideably engaging the trip linkage, wherein: when the RCBO is switched from an off state to an on state by means of the actuator lever, elastic potential energy is stored in the spring of the actuator lever; and when the RCBO is tripped from the on state to the off state the elastic potential of the actuator lever is converted into kinetic energy of the reset linkage and trip linkage which in turn is converted into elastic potential energy of the spring within the magnetic relay. at least one phase circuit (20, 21); a neutral circuit; a current sense toroid through which the at least one phase circuit and neutral circuit pass to form a primary winding; contact means to make or break the at least one phase circuit (20,21); a spring loaded actuator lever for operating the contact means via an actuator linkage and actuator mechanism with overload linkage; a magnetic relay with two trigger terminal inputs; a trip linkage slideably engaging the magnetic relay and the actuator mechanism; a secondary winding on said sense toroid connected to said magnetic relay trigger terminal inputs; and when a current imbalance between the at least one phase circuit (20, 21) and neutral circuit exists, current is induced in the secondary winding via the sense toroid sufficient to actuate the magnetic relay to release the elastic potential energy stored in a spring within the magnetic relay to provide the trip linkage with sufficient kinetic energy to trigger the overload linkage of the actuator mechanism and break the contact means, characterised in that the RCBO comprises a reset linkage connected at a proximal end to the actuator lever and at a distal end slideably engaging the trip linkage, wherein: when the RCBO is switched from an off state to an on state by means of the actuator lever, elastic potential energy is stored in the spring of the actuator lever; and when the RCBO is tripped from the on state to the off state the elastic potential of the actuator lever is converted into kinetic energy of the reset linkage and trip linkage which in turn is converted into elastic potential energy of the spring within the magnetic relay. when the RCBO is switched from an off state to an on state by means of the actuator lever, elastic potential energy is stored in the spring of the actuator lever; and when the RCBO is tripped from the on state to the off state the elastic potential of the actuator lever is converted into kinetic energy of the reset linkage and trip linkage which in turn is converted into elastic potential energy of the spring within the magnetic relay.