A gas turbine engine having a mid-plane trim balance rotor disc and a stator assembly, the stator assembly comprising: an inner diameter ring assembly, comprising a seal ring having a seal ring aperture extending therethrough along a radial axis, wherein the seal ring is configured to mount around the mid-plane trim balance rotor disc, and the seal ring aperture is configured to, when the seal ring is mounted around the mid-plane trim balance rotor disc, provide access to the mid-plane trim balance rotor disc along the radial axis, an outer diameter ring assembly that is concentric with the inner diameter ring assembly and has a larger diameter than the inner diameter ring assembly, wherein the outer diameter ring assembly has an outer diameter ring assembly aperture (312, 322) that is aligned with the seal ring aperture along the radial axis; a plurality of fixed stator vanes each comprising an airfoil that extends between the inner diameter ring assembly and the outer diameter ring assembly; and a removable stator vane configured to be removed from the stator assembly by being pulled radially outward along the radial axis, the removable stator vane comprising: an airfoil extending between the inner diameter ring assembly and the outer diameter ring assembly along the radial axis; a button; and a platform that is configured to be seated within the outer diameter ring assembly aperture (312, 322) when the removable stator vane is seated within the stator assembly; characterised in that the inner diameter ring assembly further comprises a shroud ring mounted around the seal ring, the shroud ring having a shroud ring aperture that is aligned with the seal ring aperture along the radial axis; labyrinth seals located on the mid-plane trim balance rotor disc underneath the seal ring preventing fluid passage from one side of the seal ring to the other side of the seal ring along the longitudinal axis of the stator assembly; a profile of the outer diameter ring assembly aperture (312, 322) corresponds to a profile of the platform to form an interference fit with the platform; and in that the profile of the button is sized and shaped to match the profile of the shroud ring aperture so as to form an interference fit such that, when the removable stator vane is seated within the stator assembly, the button completely fills the shroud ring aperture and covers the seal ring aperture restricting fluid passage from one side of the seal ring to the other side of the seal ring along the radial axis. an inner diameter ring assembly, comprising a seal ring having a seal ring aperture extending therethrough along a radial axis, wherein the seal ring is configured to mount around the mid-plane trim balance rotor disc, and the seal ring aperture is configured to, when the seal ring is mounted around the mid-plane trim balance rotor disc, provide access to the mid-plane trim balance rotor disc along the radial axis, an outer diameter ring assembly that is concentric with the inner diameter ring assembly and has a larger diameter than the inner diameter ring assembly, wherein the outer diameter ring assembly has an outer diameter ring assembly aperture (312, 322) that is aligned with the seal ring aperture along the radial axis; a plurality of fixed stator vanes each comprising an airfoil that extends between the inner diameter ring assembly and the outer diameter ring assembly; and a removable stator vane configured to be removed from the stator assembly by being pulled radially outward along the radial axis, the removable stator vane comprising: an airfoil extending between the inner diameter ring assembly and the outer diameter ring assembly along the radial axis; a button; and a platform that is configured to be seated within the outer diameter ring assembly aperture (312, 322) when the removable stator vane is seated within the stator assembly; an airfoil extending between the inner diameter ring assembly and the outer diameter ring assembly along the radial axis; a button; and a platform that is configured to be seated within the outer diameter ring assembly aperture (312, 322) when the removable stator vane is seated within the stator assembly; characterised in that the inner diameter ring assembly further comprises a shroud ring mounted around the seal ring, the shroud ring having a shroud ring aperture that is aligned with the seal ring aperture along the radial axis; labyrinth seals located on the mid-plane trim balance rotor disc underneath the seal ring preventing fluid passage from one side of the seal ring to the other side of the seal ring along the longitudinal axis of the stator assembly; a profile of the outer diameter ring assembly aperture (312, 322) corresponds to a profile of the platform to form an interference fit with the platform; and in that the profile of the button is sized and shaped to match the profile of the shroud ring aperture so as to form an interference fit such that, when the removable stator vane is seated within the stator assembly, the button completely fills the shroud ring aperture and covers the seal ring aperture restricting fluid passage from one side of the seal ring to the other side of the seal ring along the radial axis.