A turbine of a gas turbine engine, the turbine comprising a stationary shroud ring having an inner shroud segment, the inner shroud segment comprising a cooling configuration in which crossflow channels are configured to receive and direct a coolant through an interior of the inner shroud segment, characterised in that the crossflow channels are disposed between troughs extending lengthwise in parallel to the crossflow channels; wherein each crossflow channel: has a length defined as a distance in a circumferential direction between an upstream end and a downstream end of the crossflow channel; has a width defined as a distance in an axial direction between opposing sides of the crossflow channel; has a height defined as a distance in a radial direction between a floor and a ceiling of the crossflow channel; comprises a junction point at which the crossflow channel has a minimum cross-sectional flow area, the junction point located between the upstream and downstream ends (61, 62) and dividing the crossflow channel lengthwise into upstream and downstream sections (66, 67), the upstream section extending between the upstream end and the junction point and the downstream section extending between the junction point and the downstream end; and comprises a cross-sectional flow area that varies lengthwise such that a cross-sectional flow area of the upstream section continuously decreases between the upstream end and the junction point, and a cross-sectional flow area of the downstream section continuously increases between the junction point and the downstream end; wherein each trough: elongates between ends that define a length of the trough in the circumferential direction; has a width defined as a distance in the axial direction between opposing sides of the trough; has a depth defined as a distance in the radial direction between a surrounding surface of a floor of an outboard face of the inner shroud segment and a lowest point within the trough; and wherein each of the troughs comprise a width and depth that varies along the length of the trough. has a length defined as a distance in a circumferential direction between an upstream end and a downstream end of the crossflow channel; has a width defined as a distance in an axial direction between opposing sides of the crossflow channel; has a height defined as a distance in a radial direction between a floor and a ceiling of the crossflow channel; comprises a junction point at which the crossflow channel has a minimum cross-sectional flow area, the junction point located between the upstream and downstream ends (61, 62) and dividing the crossflow channel lengthwise into upstream and downstream sections (66, 67), the upstream section extending between the upstream end and the junction point and the downstream section extending between the junction point and the downstream end; and comprises a cross-sectional flow area that varies lengthwise such that a cross-sectional flow area of the upstream section continuously decreases between the upstream end and the junction point, and a cross-sectional flow area of the downstream section continuously increases between the junction point and the downstream end; wherein each trough: elongates between ends that define a length of the trough in the circumferential direction; has a width defined as a distance in the axial direction between opposing sides of the trough; has a depth defined as a distance in the radial direction between a surrounding surface of a floor of an outboard face of the inner shroud segment and a lowest point within the trough; and wherein each of the troughs comprise a width and depth that varies along the length of the trough. elongates between ends that define a length of the trough in the circumferential direction; has a width defined as a distance in the axial direction between opposing sides of the trough; has a depth defined as a distance in the radial direction between a surrounding surface of a floor of an outboard face of the inner shroud segment and a lowest point within the trough; and wherein each of the troughs comprise a width and depth that varies along the length of the trough.