A tube closure defines a lumen having a crease initiation region 120 between a first section 116 and a second section 118. A fold occurs in the crease initiation region upon relative rotation of the first and second sections 116 and 118. In the open condition (fig 7A), there is a flow path between the first and second sections 116 and 118, which is shut off when in the closed condition (fig 7B). The crease initiation region 120 may have a protrusion lip 204, 206 to help seal the closure when folded. The protrusion may extend only partially around the interior of the crease initiation region 120, fully around the interior, or may be an insert (figure 13). The protrusion 204, 206 may press against an interior surface of the tube when folded. The crease initiation region 120 may have local thinning of the wall, and the first and second sections 116, 118 may have internal or external stiffening ribs (eg fig 11). The tube closure may have a lens cross-section. The tube closure may be locked in the closed position, and can be urged into the open or closed positions. The tube may have a mouthpiece, e.g. when being used to seal a food or drink container (e.g. figure 25). The closure may be used as a shut off valve for a hose (figure 39) or toilet cistern flush (figure 31).
