An actuator system comprising: - a controlled element configured for rotary movement about a first axis relative to a reference structure; - a linkage system (160, 190, 121, 122, 123, 141, 142, 143) connected to the controlled element and the reference structure; - a first rotary actuator configured and arranged to power a first degree of freedom (123 relative to 122) of the linkage system (160, 190, 121, 122, 123, 141, 142, 143); - a second rotary actuator configured and arranged to power a second degree of freedom (143 relative to 142) of the linkage system (160, 190, 121, 122, 123, 141, 142, 143), the first degree of freedom and the second degree of freedom being independent degrees of freedom; - the linkage system (160, 190, 121, 122, 123, 141, 142, 143) including the first rotary actuator, said first rotary actuator comprising a first member and a second member, said first member and second member being configured and arranged for relative rotary motion to each other and to the reference structure about a second axis; the first axis and the second axis not being coincident; - the linkage system (160, 190, 121, 122, 123, 141, 142, 143) further including the second rotary actuator, said second rotary actuator comprising a first member and a second member, said first member and second member being configured and arranged for relative rotary motion to each other and to the reference structure about a third axis; - the first members (123, 143) of the first and second actuators coupled such that rotation of the first member of the first rotary actuator about the second axis in a first direction causes rotation of the first member of the second rotary actuator about the third axis in a second direction; - the linkage system (160, 190, 121, 122, 123, 141, 142, 143) configured and arranged such that a first angle of rotation between the controlled element and the reference structure may be driven independently of a second angle of rotation between the first member of the first rotary actuator and the reference structure; - wherein one of the first or second rotary actuators (120, 140) is configured and arranged to drive rotation of the controlled element about the first axis when rotation of one of the second members (122, 142) relative to its respective first member (123, 143), of the other of the first or second rotary actuator (120, 140), is operatively locked. - a controlled element configured for rotary movement about a first axis relative to a reference structure; - a linkage system (160, 190, 121, 122, 123, 141, 142, 143) connected to the controlled element and the reference structure; - a first rotary actuator configured and arranged to power a first degree of freedom (123 relative to 122) of the linkage system (160, 190, 121, 122, 123, 141, 142, 143); - a second rotary actuator configured and arranged to power a second degree of freedom (143 relative to 142) of the linkage system (160, 190, 121, 122, 123, 141, 142, 143), the first degree of freedom and the second degree of freedom being independent degrees of freedom; - the linkage system (160, 190, 121, 122, 123, 141, 142, 143) including the first rotary actuator, said first rotary actuator comprising a first member and a second member, said first member and second member being configured and arranged for relative rotary motion to each other and to the reference structure about a second axis; the first axis and the second axis not being coincident; - the linkage system (160, 190, 121, 122, 123, 141, 142, 143) further including the second rotary actuator, said second rotary actuator comprising a first member and a second member, said first member and second member being configured and arranged for relative rotary motion to each other and to the reference structure about a third axis; - the first members (123, 143) of the first and second actuators coupled such that rotation of the first member of the first rotary actuator about the second axis in a first direction causes rotation of the first member of the second rotary actuator about the third axis in a second direction; - the linkage system (160, 190, 121, 122, 123, 141, 142, 143) configured and arranged such that a first angle of rotation between the controlled element and the reference structure may be driven independently of a second angle of rotation between the first member of the first rotary actuator and the reference structure; - wherein one of the first or second rotary actuators (120, 140) is configured and arranged to drive rotation of the controlled element about the first axis when rotation of one of the second members (122, 142) relative to its respective first member (123, 143), of the other of the first or second rotary actuator (120, 140), is operatively locked.