An access control system (1) for restricting access through a passageway (38), the access control system (1) comprising: a shaft (10) which is rotatable about a central axis (A); a barrier (12) fixed to the shaft (10) to rotate therewith; and a brake assembly (14) for applying a braking force to the shaft (10), wherein the brake assembly (14) comprises: ; a sun gear (18) which is rotatable about the central axis (A) of the shaft (10); a carrier (16) and a ring gear (20), wherein one of the carrier or the ring gear is fixed against rotation and wherein the other of the carrier or ring gear is connected to the shaft to rotate therewith; a plurality of planet gears (22) rotatably connected to the carrier (16) so as to permit rotation relative to the carrier (16), each planet gear (22) being disposed between the sun gear (18) and the ring gear (20) and engaging with each of the sun gear (18) and the ring gear (20); and an electromagnetic brake (24) comprising an electromagnet (32) and an armature (26), the armature (26) being connected to or integral with the sun gear (18) to rotate therewith, wherein at least one of the electromagnet (32) or the armature (26) is moveable between an operative position in which the electromagnet (32) and the armature (26) are in contact, and an inoperative position in which the electromagnet (32) is spaced from the armature (26).