The invention provides a valve assembly comprising a conduit with a bore 1b for passage of fluid therethrough. The valve assembly also comprises a sealing member that is movable within the conduit to open and close the bore. The seal assembly has a valve seat on which the sealing member seals when the bore is closed, and wherein the valve seat is movable within the conduit. The invention also provides a valve assembly comprising a sealing member, a first valve seat for the sealing member, and a second valve seat for the sealing member. The valve assemblies can be resettable. The invention further provides a flapper valve assembly wherein the flapper is pivotable through more than 90° and a bi-directional flapper valve assembly.