An accessory (14) for partially enclosing a shaft of an endoscope is disclosed. The accessory (14) defines a first space (36) for accommodating the shaft and a second space (32) for defining a conduit along the shaft. An outer surface (16) of the accessory around the first and second spaces is centred on a first longitudinal axis (20), and the first space (36) is centred on a second longitudinal axis (22) spaced relative to the first longitudinal axis (20). The first space (36) is open to one side (38), so that the accessory only partially encloses the shaft when placed around it.
