An axial flow turbine blade and diaphragm construction comprises an annulus of static turbine blades 20 and inner and outer spacer rings 40, 42 having apertures 41, 43 shaped to accommodate inner and outer platform portions 22, 23 of the blades, whereby the platform portions and the spacer rings together form inner and outer port walls of the turbine diaphragm. A particular feature of the blades is that the inner and outer platform portions 22 and 23 have straight side edges 22B, 22C and 23B, 23C, which are joined to each other by curved leading edges 22D and 23D that in plan view have a shape that follows the edge of the corner fillet 24 in the region of the leading edge 26 of the aerofoil 21.