Control valve assembly and fuel injector incorporating a control valve assembly

A control valve assembly for controlling fuel pressure in a control chamber of a fuel injector, the control valve assembly comprising a valve member arranged in a bore provided in a valve housing wherein the valve member moves between a closed position which prevents fluid communication between the control chamber and a low pressure drain and an open position which provides fluid communication between the control chamber and the low pressure drain, at least one of the valve member and the valve housing being moveable with respect to the other, wherein the valve member comprises a fuel-receiving cavity which receives fuel that distorts at least a portion of the valve member so as to increase an external dimension thereof such that the fuel-receiving cavity is in fluid communication with the low pressure drain when the valve member is in the open position and such that the fuel-receiving cavity is not in fluid communication with the low pressure drain when the valve member is in the closed position, wherein the fuel-receiving cavity is a drilled cavity which extends into the valve member from a first end and wherein the drilled cavity is plugged by an insert which prevents fluid communication through the drilled cavity from the fuel receiving cavity to the first end.