A multiple-stage valve system including a pilot fluid supply and a process fluid supply, the multiple-stage valve system comprising: a first pilot valve including a first port in fluid communication with the pilot fluid supply and a second port selectively in fluid communication with the first port; a second pilot valve including: a first port in fluid communication with the process fluid supply; a second port selectively in fluid communication with the first port; a first pressure-actuated biasing member in fluid communication with the process fluid supply; a second pressure-actuated biasing member in fluid communication with the second port of the first pilot valve; a main control valve including: a first port in fluid communication with the process fluid supply; a second port selectively in fluid communication with the first port; a first pressure-actuated biasing member in fluid communication with the process fluid supply; and a second pressure-actuated biasing member in fluid communication with the second port of the second pilot valve, characterised in that the multiple-stage valve system is configured such that process fluid from the process fluid supply acts on both the first pressure actuated biasing member and the second pressure-actuated biasing member of the main control valve, such that the ratio of forces acting on the two biasing members (225, 226) is constant and independent of the process fluid pressure. a first pilot valve including a first port in fluid communication with the pilot fluid supply and a second port selectively in fluid communication with the first port; a second pilot valve including: a first port in fluid communication with the process fluid supply; a second port selectively in fluid communication with the first port; a first pressure-actuated biasing member in fluid communication with the process fluid supply; a second pressure-actuated biasing member in fluid communication with the second port of the first pilot valve; a main control valve including: a first port in fluid communication with the process fluid supply; a second port selectively in fluid communication with the first port; a first pressure-actuated biasing member in fluid communication with the process fluid supply; and a second pressure-actuated biasing member in fluid communication with the second port of the second pilot valve, characterised in that the multiple-stage valve system is configured such that process fluid from the process fluid supply acts on both the first pressure actuated biasing member and the second pressure-actuated biasing member of the main control valve, such that the ratio of forces acting on the two biasing members (225, 226) is constant and independent of the process fluid pressure. a first port in fluid communication with the process fluid supply; a second port selectively in fluid communication with the first port; a first pressure-actuated biasing member in fluid communication with the process fluid supply; a second pressure-actuated biasing member in fluid communication with the second port of the first pilot valve; a main control valve including: a first port in fluid communication with the process fluid supply; a second port selectively in fluid communication with the first port; a first pressure-actuated biasing member in fluid communication with the process fluid supply; and a second pressure-actuated biasing member in fluid communication with the second port of the second pilot valve, a first port in fluid communication with the process fluid supply; a second port selectively in fluid communication with the first port; a first pressure-actuated biasing member in fluid communication with the process fluid supply; and a second pressure-actuated biasing member in fluid communication with the second port of the second pilot valve, characterised in that the multiple-stage valve system is configured such that process fluid from the process fluid supply acts on both the first pressure actuated biasing member and the second pressure-actuated biasing member of the main control valve, such that the ratio of forces acting on the two biasing members (225, 226) is constant and independent of the process fluid pressure.