Abstract: A control method for controlling the fuel pressure within the common rail or accumulator of a fuel system whilst an associated engine is operating, the fuel system including a plurality of individually actuable fuel injectors arranged to receive fuel from the common rail, each injector including a control valve operable to control the fuel pressure within a control chamber, fuel escaping from the control chamber being returned to a fuel reservoir, the method comprising: monitoring the fuel pressure within the common rail; controlling the rate of fuel supply to the common rail; and relieving the common rail fuel pressure in the event that the common rail fuel pressure exceeds a predetermined threshold by actuating the control valve of at least one of the injectors to allow fuel to flow from the common rail, through the control chamber of the injector to the fuel reservoir, the control valve(s) being arranged to control the fuel pressure within the control chamber(s) of the said at least one of the injectors