Conventional linkages between bicycle handlebar-mounted controls and rear brakes and gears are unable to accommodate unlimited rotation of the handlebars as is required on some so-called “freestyle” bicycles. A prior attempt to solve the problem employs a linkage comprising a bearing having two parts that are relatively rotatable about an axis. However this proposal is unable to handle situations where there are two or more mechanisms to be controlled e.g. a rear brake and a gear. Another problem is that dirt between the bearing surfaces may cause the bearing to jam. The invention provides pins (15C) that fit into slots (8A) for restricting rotation, relative to the handlebars, of a first bearing part (15A) and pins (15F) that fit in slots (9A) for restricting rotation, relative to the bicycle frame, of a second bearing part (15B). The aforementioned slots are formed in cylindrical guide walls not visible in FIG. 5. The use of the bearing (15) avoids any twisting of Bowden cables (7A, 7B) or the like such as are used on conventional linkages and, if any grit were to find its way between the two parts (15A, 15B) of the bearing, the latter are nevertheless forced to rotate relative to each other thus avoiding seizing of the bearing. The invention is not exclusively applicable to bicycles and can be used in linkages between parts of robotic machinery and other equipment.