An apparatus for constraining a device (7) to pivot about a remote centre of motion (0). The apparatus includes a first member (1). A second member (2) is pivotally connected to the first member at a first pivotal connection (1). A third member (3) is pivotally connected to the first member at a second pivotal connection (2). A fourth member (4) is pivotally connected to the second member at a third pivotal connection (3). A fifth member (5) is pivotally connected to the third member at a fourth pivotal connection (4). A sixth member 6 (a) is pivotally connected to the fourth member at a fifth pivotal connection 5, (b) is pivotally connected to the fifth member at a sixth pivotal connection 6, and (c) is, or is fixable or integral to, the device. The apparatus further includes a mechanism for in substance maintaining a notional straight line, from the first pivotal connection to the third pivotal connection, parallel to a notional straight line from the second pivotal connection to the fourth pivotal connection. The apparatus further includes a mechanism for in substance maintaining a notional straight line, from the third pivotal connection to the fifth pivotal connection, parallel to a notional straight line from the fourth pivotal connection to the sixth pivotal connection. Each pivotal connection has a respective pivot axis. The pivot axes of the first pivotal connection and the second pivotal connection in substance lie in a common plane (9). The pivot axes of the third pivotal connection and the fourth pivotal connection in substance lie in another common plane (10). The pivot axes of the fifth pivotal connection and the sixth pivotal connection in substance lie in another common plane (11). The common planes in substance intersect at the remote centre of motion.Linvention concerne un appareil pour contraindre un dispositif (7) à pivoter autour dun centre de rotation distant (0). Cet appareil comprend un premier élément (1). Un second élément (2) est relié de
