A coupling for vacuum-insulated piping, the coupling comprising: First and second parts for forming the coupling, a first seal member for forming a seal between the first and second parts, each of the first and second parts comprising an inner portion (6, 7) for connection to an inner part (104, 204) of a vacuum-insulated pipe and an outer portion (18, 20) for connection to an outer, low pressure part of a vacuum-insulated pipe, the inner portions of the first and second parts being suitable for forming an inner region for the passage of fluid therethrough, the outer portion of the first part defining a first outer region and the outer portion of the second part defining a second outer region; a sensor outlet for a leak detection sensor; a first flow path for permitting flow of fluid from the inner region to the sensor outlet in the event of failure of the first seal member; and a second flow path for permitting flow of fluid from the first outer region or the second outer region to the sensor outlet in the event that the pressure in said first or second outer region is greater than a predetermined pressure, characterised in that the second flow path is provided with a non-return valve for permitting flow of fluid from the respective first outer region or the second outer region to the sensor outlet in the event that the pressure in said first or second outer region is greater than a predetermined pressure, and inhibiting flow of fluid from the sensor outlet to the respective first or second outer region in the event that the pressure in said respective first or second outer region is at or below a predetermined pressure. First and second parts for forming the coupling, a first seal member for forming a seal between the first and second parts, each of the first and second parts comprising an inner portion (6, 7) for connection to an inner part (104, 204) of a vacuum-insulated pipe and an outer portion (18, 20) for connection to an outer, low pressure part of a vacuum-insulated pipe, the inner portions of the first and second parts being suitable for forming an inner region for the passage of fluid therethrough, the outer portion of the first part defining a first outer region and the outer portion of the second part defining a second outer region; each of the first and second parts comprising an inner portion (6, 7) for connection to an inner part (104, 204) of a vacuum-insulated pipe and an outer portion (18, 20) for connection to an outer, low pressure part of a vacuum-insulated pipe, the inner portions of the first and second parts being suitable for forming an inner region for the passage of fluid therethrough, the outer portion of the first part defining a first outer region and the outer portion of the second part defining a second outer region; a sensor outlet for a leak detection sensor; a first flow path for permitting flow of fluid from the inner region to the sensor outlet in the event of failure of the first seal member; and a second flow path for permitting flow of fluid from the first outer region or the second outer region to the sensor outlet in the event that the pressure in said first or second outer region is greater than a predetermined pressure, characterised in that the second flow path is provided with a non-return valve for permitting flow of fluid from the respective first outer region or the second outer region to the sensor outlet in the event that the pressure in said first or second outer region is greater than a predetermined pressure, and inhibiting flow of fluid from the sensor outlet to the respective first or second outer region in the event that the pressure in said respective first or second outer region is at or below a predetermined pressure.