A composite component, such as an aerofoil component for a gas turbine engine, comprises a body and a platform which are formed from respective body and platform preforms. The body preform includes fibers which are directed laterally of the preform, forming a cavity in the end of the preform. The platform preform includes a projection constituting a deltoid filler which is received in the cavity. The projection includes a 3D woven structure of reinforcement fibers so that the cavity is occupied by fibers to give the platform a generally uniform volume fraction. A further platform preform fits over the body preform so that the lateral fibers are sandwiched between the platform preforms.