A leaf seal assembly for providing a fluidic seal between a first member and a second member, comprising: first and second cover plates (3, 5) defining a channel therebetween, the first cover plate having a first inner edge and the second cover plate having a second inner edge; and a plurality of leaf elements located within the channel, each leaf element having first and second leaf edges (11 a, 11 b) adjacent to the first and second cover plates respectively, wherein a projecting portion of each leaf element extends beyond the first and second inner edges; wherein there is a first gap between the first leaf edges of the plurality of leaf elements and an inner surface of the first cover plate and a second gap between the second leaf edges of the plurality of leaf elements and an inner surface of the second cover plate; characterised that the size of the first gap, the size of the second gap, and the positioning of their respective cover plates (3,5) is chosen such that when the seal assembly is located between a first member and a second member; a fluid flow in a first direction from the first cover plate side of the seal assembly to the second cover plate side of the seal assembly causes the plurality of leaf elements to move away from the first member to create a fluid passage between the plurality of leaf elements and the first member thereby allowing a flow of fluid through the seal in the first direction; and a fluid flow in a second direction from the second cover plate side of the seal assembly to the first cover plate side of the assembly causes the plurality of leaf elements to move towards the first member such that a third leaf edge of the projecting portion of each of the leaf elements contacts the first member, thereby opposing the flow of fluid through the seal in the second direction. first and second cover plates (3, 5) defining a channel therebetween, the first cover plate having a first inner edge and the second cover plate having a second inner edge; and a plurality of leaf elements located within the channel, each leaf element having first and second leaf edges (11 a, 11 b) adjacent to the first and second cover plates respectively, wherein a projecting portion of each leaf element extends beyond the first and second inner edges; wherein there is a first gap between the first leaf edges of the plurality of leaf elements and an inner surface of the first cover plate and a second gap between the second leaf edges of the plurality of leaf elements and an inner surface of the second cover plate; characterised that the size of the first gap, the size of the second gap, and the positioning of their respective cover plates (3,5) is chosen such that when the seal assembly is located between a first member and a second member; a fluid flow in a first direction from the first cover plate side of the seal assembly to the second cover plate side of the seal assembly causes the plurality of leaf elements to move away from the first member to create a fluid passage between the plurality of leaf elements and the first member thereby allowing a flow of fluid through the seal in the first direction; and a fluid flow in a second direction from the second cover plate side of the seal assembly to the first cover plate side of the assembly causes the plurality of leaf elements to move towards the first member such that a third leaf edge of the projecting portion of each of the leaf elements contacts the first member, thereby opposing the flow of fluid through the seal in the second direction.