A gas turbine engine having a bypass duct defined at its outer radius by a nacelle, and a thrust reverser unit, the thrust reverser unit being operable in either a stowed configuration or a deployed configuration and comprising: a first element; a second element; and a joint that rotatably attaches the first element to the second element, wherein: in the stowed configuration the first and second elements are contained within the nacelle; the first element is arranged to rotate about the joint relative to the second element between the stowed configuration and the deployed configuration, such that in the deployed configuration the first element extends across the bypass duct; the first and second elements both have flow passages (112, 122) through which gas can pass, such that in the deployed configuration, in use at least some of the flow through the bypass duct is directed through both the first element and the second element; characterized in that: the thrust reverser unit further comprises an actuator arranged to deploy the thrust reverser unit from the stowed configuration to the deployed configuration in a two-stage process comprising translating both the first and second elements followed by rotating the first element about the joint into its deployed position across the bypass duct. a first element; a second element; and a joint that rotatably attaches the first element to the second element, wherein: in the stowed configuration the first and second elements are contained within the nacelle; the first element is arranged to rotate about the joint relative to the second element between the stowed configuration and the deployed configuration, such that in the deployed configuration the first element extends across the bypass duct; the first and second elements both have flow passages (112, 122) through which gas can pass, such that in the deployed configuration, in use at least some of the flow through the bypass duct is directed through both the first element and the second element; characterized in that: the thrust reverser unit further comprises an actuator arranged to deploy the thrust reverser unit from the stowed configuration to the deployed configuration in a two-stage process comprising translating both the first and second elements followed by rotating the first element about the joint into its deployed position across the bypass duct. in the stowed configuration the first and second elements are contained within the nacelle; the first element is arranged to rotate about the joint relative to the second element between the stowed configuration and the deployed configuration, such that in the deployed configuration the first element extends across the bypass duct; the first and second elements both have flow passages (112, 122) through which gas can pass, such that in the deployed configuration, in use at least some of the flow through the bypass duct is directed through both the first element and the second element; characterized in that: the thrust reverser unit further comprises an actuator arranged to deploy the thrust reverser unit from the stowed configuration to the deployed configuration in a two-stage process comprising translating both the first and second elements followed by rotating the first element about the joint into its deployed position across the bypass duct. the thrust reverser unit further comprises an actuator arranged to deploy the thrust reverser unit from the stowed configuration to the deployed configuration in a two-stage process comprising translating both the first and second elements followed by rotating the first element about the joint into its deployed position across the bypass duct.