A method of extending the load range for viable operating W V of a steam turbine power plant comprising a boiler with a superheater for supplying superheated steam to a steam turbine, the steam turbine having a required minimum viable temperature T V of steam entering the steam turbine, the load range for viable operating W V of the steam turbine power plant being extended by means of controllably using an auxiliary superheating chamber comprising an auxiliary superheater to further superheat steam; the method comprising: - determining the temperature T of the steam entering the steam turbine; - when the temperature T of the steam entering the steam turbine is above an alert temperature T A, which alert temperature T A is higher than the required minimum viable temperature T V; • burning fuel in the boiler to generate thermal energy to be transferred into steam in the superheater to generate superheated steam satisfying the required minimum viable temperature T V of the steam entering the steam turbine; • conveying the superheated steam from the superheater to the auxiliary superheater of the auxiliary superheating chamber; • burning fuel with a burner in the auxiliary superheating chamber to keep the auxiliary superheating chamber in a hot standby temperature, which temperature is higher than ambient temperature and not higher than the temperature of the superheated steam entering the auxiliary superheater; • conveying the superheated steam from the auxiliary superheater to the steam turbine; and - when the temperature T of the steam entering the steam turbine is at or below the alert temperature T A, • burning fuel in the boiler to generate thermal energy to be transferred into steam in the superheater to generate superheated steam; • conveying the superheated steam from the superheater to the auxiliary superheater of the auxiliary superheating chamber; • further superheating the superheated steam by burning fuel with a burner in the auxiliary superheating chamber to generate thermal energy to be transferred into the superheated steam in the auxiliary superheater such that the required minimum viable temperature T V of steam entering the steam turbine is satisfied; • conveying the superheated steam from the auxiliary superheater to the steam turbine. - determining the temperature T of the steam entering the steam turbine; - when the temperature T of the steam entering the steam turbine is above an alert temperature T A, which alert temperature T A is higher than the required minimum viable temperature T V; • burning fuel in the boiler to generate thermal energy to be transferred into steam in the superheater to generate superheated steam satisfying the required minimum viable temperature T V of the steam entering the steam turbine; • conveying the superheated steam from the superheater to the auxiliary superheater of the auxiliary superheating chamber; • burning fuel with a burner in the auxiliary superheating chamber to keep the auxiliary superheating chamber in a hot standby temperature, which temperature is higher than ambient temperature and not higher than the temperature of the superheated steam entering the auxiliary superheater; • conveying the superheated steam from the auxiliary superheater to the steam turbine; and • burning fuel in the boiler to generate thermal energy to be transferred into steam in the superheater to generate superheated steam satisfying the required minimum viable temperature T V of the steam entering the steam turbine; • conveying the superheated steam from the superheater to the auxiliary superheater of the auxiliary superheating chamber; • burning fuel with a burner in the auxiliary superheating chamber to keep the auxiliary superheating chamber in a hot standby temperature, which temperature is higher than ambient temperature and not higher than the temperature of the superheated steam entering the auxiliary superheater; • conveying the superheated steam from the auxiliary superheater to the steam turbine; and - when the temperature T of the steam entering the steam turbine is at or below the alert temperature T A, • burning fuel in the boiler to generate thermal energy to be transferred into steam in the superheater to generate superheated steam; • conveying the superheated steam from the superheater to the auxiliary superheater of the auxiliary superheating chamber; • further superheating the superheated steam by burning fuel with a burner in the auxiliary superheating chamber to generate thermal energy to be transferred into the superheated steam in the auxiliary superheater such that the required minimum viable temperature T V of steam entering the steam turbine is satisfied; • conveying the superheated steam from the auxiliary superheater to the steam turbine. • burning fuel in the boiler to generate thermal energy to be transferred into steam in the superheater to generate superheated steam; • conveying the superheated steam from the superheater to the auxiliary superheater of the auxiliary superheating chamber; • further superheating the superheated steam by burning fuel with a burner in the auxiliary superheating chamber to generate thermal energy to be transferred into the superheated steam in the auxiliary superheater such that the required minimum viable temperature T V of steam entering the steam turbine is satisfied; • conveying the superheated steam from the auxiliary superheater to the steam turbine.