A valve arrangement for use in limiting the pressure of fuel within an accumulator volume of an accumulator fuel system to a predetermined threshold level, the valve arrangement comprising: a valve outlet (64, 66) for communication with a low pressure drain; a valve housing provided with a valve housing bore for receiving fuel from the accumulator volume; a valve member comprising a ball slidably received in a first section of the housing bore, said member having a closed position in which it is engaged with a valve seating defined by the valve housing bore to prevent fuel flow from the accumulator volume to the valve outlet (64, 66); biasing means for urging the valve member towards the valve seating; a first restricted flow means for restricting the flow of fuel between the accumulator volume and the valve outlet (64, 66) during a first stage of valve opening movement as soon as the valve member is lifted from the valve seating; the valve arrangement being characterised in that it further comprises: a second restricted flow means effective during a second stage of valve opening movement which follows the first stage to provide a greater restriction than during the first stage; and a third restricted flow means effective during a third stage of valve opening movement which follows the second stage to provide a variable restriction to fuel flow dependent on the extent of opening movement of the valve member, wherein each of the first, second and third restricted flow means (80, 82, 84) is defined between the ball and the first section of the valve housing bore and, the valve seating is located on a first conical section which is defined by the valve housing bore and, the first restricted flow means is defined between the valve member and the valve seating and, the third restricted flow means is defined by a second conical section, which is defined by the valve housing bore and, the first and second conical sections (54, 58) define an intermediate section therebetween, wherein the intermediate section cooperates with the valve member to define the second restricted flow means. a valve outlet (64, 66) for communication with a low pressure drain; a valve housing provided with a valve housing bore for receiving fuel from the accumulator volume; a valve member comprising a ball slidably received in a first section of the housing bore, said member having a closed position in which it is engaged with a valve seating defined by the valve housing bore to prevent fuel flow from the accumulator volume to the valve outlet (64, 66); biasing means for urging the valve member towards the valve seating; a first restricted flow means for restricting the flow of fuel between the accumulator volume and the valve outlet (64, 66) during a first stage of valve opening movement as soon as the valve member is lifted from the valve seating; the valve arrangement being characterised in that it further comprises: a second restricted flow means effective during a second stage of valve opening movement which follows the first stage to provide a greater restriction than during the first stage; and a third restricted flow means effective during a third stage of valve opening movement which follows the second stage to provide a variable restriction to fuel flow dependent on the extent of opening movement of the valve member, wherein each of the first, second and third restricted flow means (80, 82, 84) is defined between the ball and the first section of the valve housing bore and, the valve seating is located on a first conical section which is defined by the valve housing bore and, the first restricted flow means is defined between the valve member and the valve seating and, the third restricted flow means is defined by a second conical section, which is defined by the valve housing bore and, the first and second conical sections (54, 58) define an intermediate section therebetween, wherein the intermediate section cooperates with the valve member to define the second restricted flow means.