A seal assembly for a gas turbine engine comprising: a seal (69; 169; 269) including a main body (170; 270) extending circumferentially between opposed mate faces (178; 278), the main body including a sealing portion (177; 277) and an engagement portion (179; 279) extending outwardly from sealing portion along at least one of the mate faces; and wherein the main body includes: a core (192; 292) including one or more core plies having a first fiber construction comprising substantially continuous fibers and arranged to establish an internal cavity; an overwrap (194; 294) including one or more overwrap plies having a second fiber construction comprising substantially continuous fibers and arranged to follow a perimeter of the one or more core plies to establish the engagement portion and the sealing portion, and the second fiber construction differing from the first fiber construction; and a platform insert (197; 297) extending between portions of the core and the overwrap to establish the sealing portion, and the platform insert having a construction that differs from the first and second fiber construction, characterised in that the platform insert includes at least one intermediate ply situated between portions of the core and the overwrap to establish the sealing portion, and the at least one intermediate ply has a third fiber construction of substantially discontinuous fibers. a seal (69; 169; 269) including a main body (170; 270) extending circumferentially between opposed mate faces (178; 278), the main body including a sealing portion (177; 277) and an engagement portion (179; 279) extending outwardly from sealing portion along at least one of the mate faces; and wherein the main body includes: a core (192; 292) including one or more core plies having a first fiber construction comprising substantially continuous fibers and arranged to establish an internal cavity; an overwrap (194; 294) including one or more overwrap plies having a second fiber construction comprising substantially continuous fibers and arranged to follow a perimeter of the one or more core plies to establish the engagement portion and the sealing portion, and the second fiber construction differing from the first fiber construction; and a platform insert (197; 297) extending between portions of the core and the overwrap to establish the sealing portion, and the platform insert having a construction that differs from the first and second fiber construction, characterised in that the platform insert includes at least one intermediate ply situated between portions of the core and the overwrap to establish the sealing portion, and the at least one intermediate ply has a third fiber construction of substantially discontinuous fibers. a core (192; 292) including one or more core plies having a first fiber construction comprising substantially continuous fibers and arranged to establish an internal cavity; an overwrap (194; 294) including one or more overwrap plies having a second fiber construction comprising substantially continuous fibers and arranged to follow a perimeter of the one or more core plies to establish the engagement portion and the sealing portion, and the second fiber construction differing from the first fiber construction; and a platform insert (197; 297) extending between portions of the core and the overwrap to establish the sealing portion, and the platform insert having a construction that differs from the first and second fiber construction, characterised in that the platform insert includes at least one intermediate ply situated between portions of the core and the overwrap to establish the sealing portion, and the at least one intermediate ply has a third fiber construction of substantially discontinuous fibers.