A pressure independent control valve (PICV) is disclosed. The PICV has a body having a flow path extending therethrough and a cavity within the flow path to releasably receive a mechanism via an aperture. The PICV also has a cap comprising the mechanism. The cap is configured to move between a locked position where the cap is retained on the body and an unlocked position where the cap is releasable from the body. The cap is retained in the locked position by one or more bayonet fixings.