The present invention relates to adjustable flow control valves, for example to an Adjustable Pressure Limiting (APL) valve. The adjustable valve (2) described comprises a valve body (4) comprising a valve seat (6), a valve member (10) movable relative to the valve seat (6), a first valve cap (20), a second valve cap (50) and a biasing element (30) to bias the valve member (10) away from the first valve cap (20). The first valve cap (20) is movable to increase the biasing force applied by the biasing element (30). The second valve cap (50) is engageable with the first valve cap (20) to prevent such movement of the first valve cap (20) beyond a selected position, but to allow movement of the first valve cap (20) in an opposite direction, way from said position.