A valve (100) comprising a tubular body (110) closed at a proximal end (111) and open at a distal end (112), outer sealing surfaces (120, 130) provided at the proximal and distal ends for sealing against an inner surface of a tube, the body comprising a flexibly mounted leg (150) between the proximal and distal ends, the leg configured to flex outwards from the body on engagement of the open distal end with a spigot so as to open a fluid flow path through the body.