A blade for mounting on a rotor disc of a gas turbine engine includes platform segments between a airfoil and blade root and extending laterally from the blade, the platform segment having a curved profile defining a platform recess on a root side of the platform segment, the recess configured to cooperate with recesses of adjacent blades to define a blade pocket. A recessed region is defined in a rear surface of the blade root, and is configured to receive a complementary projection of the rotor disc upon mounting the blade on the rotor disc. The recessed region has a surface configured to abut a corresponding surface on the projection of the rotor disc to form a face seal. Methods of manufacturing such a rotor disc and of sealing a circumferential joint between such blades and the rotor disc are also disclosed.