A bed for a child, the bed comprising: a base forming a surface for the child to be laid on; an upper frame comprising two or more frame members at least partially forming a rim around an opening into an interior space of the bed, walls extending upwardly from the base to the upper frame, the walls extending around the surface to partially enclose the interior space of the bed; wherein one of the frame members is a movable frame member, wherein the movable frame member is movable relative to another of the frame members in order to adjust a height of a portion of the rim formed by the movable frame member relative to the base, wherein the upper frame is configured such that the movable frame member is movable between first, second and third predetermined positions at which the height of the portion of the rim is at first, second and third respective predetermined heights relative to the base, wherein the upper frame comprises a locking mechanism configured to selectively lock the movable frame member at the first and second predetermined positions, and wherein the upper frame is configured such that the position of the movable frame element is biased to move from the third predetermined position towards the first and second predetermined positions, wherein the third predetermined height is less than the first and second predetermined heights, wherein the upper frame comprises an actuator for selectively actuating the locking mechanism between a locking configuration, in which the locking mechanism is to lock the position of the movable frame member at the first or second predetermined height, and an unlocked configuration, in which the movable frame member does not become locked in the first or second predetermined positions, wherein the locking mechanism and/or the actuator is biased into the locking configuration, wherein, in a first mode of operation of the upper frame, the locking mechanism is configured to lock the position of the movable frame member at the second predetermined position when the movable frame member is at the second predetermined position, and wherein, in a second mode of operation of the upper frame, the locking mechanism is configured such that the movable frame member does not become automatically locked in the first or second predetermined positions, and wherein the locking mechanism is configured such that the movable frame member cannot be locked in the third predetermined position, characterized in that the upper frame further comprises a further actuator configured to selectively lock the actuator in the unlocked configuration. a base forming a surface for the child to be laid on; an upper frame comprising two or more frame members at least partially forming a rim around an opening into an interior space of the bed, walls extending upwardly from the base to the upper frame, the walls extending around the surface to partially enclose the interior space of the bed; wherein one of the frame members is a movable frame member, wherein the movable frame member is movable relative to another of the frame members in order to adjust a height of a portion of the rim formed by the movable frame member relative to the base, wherein the upper frame is configured such that the movable frame member is movable between first, second and third predetermined positions at which the height of the portion of the rim is at first, second and third respective predetermined heights relative to the base, wherein the upper frame comprises a locking mechanism configured to selectively lock the movable frame member at the first and second predetermined positions, and wherein the upper frame is configured such that the position of the movable frame element is biased to move from the third predetermined position towards the first and second predetermined positions, wherein the third predetermined height is less than the first and second predetermined heights, wherein the upper frame comprises an actuator for selectively actuating the locking mechanism between a locking configuration, in which the locking mechanism is to lock the position of the movable frame member at the first or second predetermined height, and an unlocked configuration, in which the movable frame member does not become locked in the first or second predetermined positions, wherein the locking mechanism and/or the actuator is biased into the locking configuration, wherein, in a first mode of operation of the upper frame, the locking mechanism is configured to lock the position of the movable frame member at the second predetermined position when the movable frame member is at the second predetermined position, and wherein, in a second mode of operation of the upper frame, the locking mechanism is configured such that the movable frame member does not become automatically locked in the first or second predetermined positions, and wherein the locking mechanism is configured such that the movable frame member cannot be locked in the third predetermined position, characterized in that the upper frame further comprises a further actuator configured to selectively lock the actuator in the unlocked configuration.