A method of operating a machine comprising a work tool and an apparatus mounted to the work tool, the apparatus comprising: a gas spring arrangement comprising a first gas chamber defined by a piston head moveably mounted inside a cylinder; a gas supply apparatus comprising at least one gas storage tank having a fixed volume and containing a gas, wherein the at least one gas storage tank is fluidly connected by a gas supply conduit to the cylinder; and a gas supply valve assembly provided in the gas supply conduit; wherein the method comprises a charging step for drawing gas from the at least one gas storage tank into the cylinder, the charging step comprising: moving the piston head in the cylinder to increase the volume of the first gas chamber to decrease a gas pressure in the at least one gas storage tank such that gas moves from the at least one gas storage tank into the cylinder; characterised in that the gas supply valve assembly is moved to: a charging configuration in which any flow through the gas supply valve assembly is in a direction from the at least one gas storage tank towards the cylinder such that the return of gas from the cylinder to the at least one gas storage tank is prevented during the charging step; or a use configuration wherein the gas supply valve assembly prevents flow therethrough. a gas spring arrangement comprising a first gas chamber defined by a piston head moveably mounted inside a cylinder; a gas supply apparatus comprising at least one gas storage tank having a fixed volume and containing a gas, wherein the at least one gas storage tank is fluidly connected by a gas supply conduit to the cylinder; and a gas supply valve assembly provided in the gas supply conduit; wherein the method comprises a charging step for drawing gas from the at least one gas storage tank into the cylinder, the charging step comprising: moving the piston head in the cylinder to increase the volume of the first gas chamber to decrease a gas pressure in the at least one gas storage tank such that gas moves from the at least one gas storage tank into the cylinder; characterised in that the gas supply valve assembly is moved to: a charging configuration in which any flow through the gas supply valve assembly is in a direction from the at least one gas storage tank towards the cylinder such that the return of gas from the cylinder to the at least one gas storage tank is prevented during the charging step; or a use configuration wherein the gas supply valve assembly prevents flow therethrough. moving the piston head in the cylinder to increase the volume of the first gas chamber to decrease a gas pressure in the at least one gas storage tank such that gas moves from the at least one gas storage tank into the cylinder; characterised in that the gas supply valve assembly is moved to: a charging configuration in which any flow through the gas supply valve assembly is in a direction from the at least one gas storage tank towards the cylinder such that the return of gas from the cylinder to the at least one gas storage tank is prevented during the charging step; or a use configuration wherein the gas supply valve assembly prevents flow therethrough. a charging configuration in which any flow through the gas supply valve assembly is in a direction from the at least one gas storage tank towards the cylinder such that the return of gas from the cylinder to the at least one gas storage tank is prevented during the charging step; or a use configuration wherein the gas supply valve assembly prevents flow therethrough.