A leaf seal is provided for effecting a seal between two coaxial, relatively rotating components. The leaf seal has an annular pack of leaves which are stacked face-to-face within the pack, and which are mountable to one of the components at respective root portions of the leaves such that the leaves extend towards the other component and respective edges of the leaves are presented for wiping contact with the other component. The pack includes a plurality of spacers, each spacer separating the root portions of neighboring leaves to form therebetween interleaf gaps which allow an axial leakage flow through the pack. The spacers are distributed around the pack such that the leaves are divided into blocks of two or more leaves sandwiched at their root portions between nearest-neighbor spacers.