A rotary actuator comprises a rotatable vane assembly mounted within a housing to define first and second chambers, wherein the rotatable vane assembly is rotatable between first and second positions. A first fluid port is in communication with the first chamber to permit an actuation fluid to be delivered to/from the first chamber, and a second fluid port is in communication with the second fluid chamber to permit actuation fluid to be delivered to/from the second fluid chamber. A sealing arrangement is provided for sealing at least one of the first and second fluid ports when the vane assembly is located in one or both of its first and second positions.