A system comprising: a cover, the cover being a substantially rigid cover and configured to close off an opening to a void having a side wall, and the cover defining a pair of opposed sides (20, 22), being an operatively top side and an opposed underside; and a locking assembly for the cover, the locking assembly comprising: a mounting arrangement mounted to the underside of the cover; a link pivotally connected to the mounting arrangement, the link defining a first end and a second, free end; a locking member carried by the second, free end of the link, the locking member being configured to frictionally engage with the side wall of the void in a locking position, in use, wherein such frictional engagement of the locking member with the side wall of the void in the locking position, in use, locks the cover; an actuating member connected to the link and accessible via the operatively top side of the cover, the actuating member being operable to displace the link relative to the mounting arrangement to cause the locking member to frictionally disengage from the side wall of the void to a disengaged position, characterized in that the actuating member is at least pivotally connected to the link. a cover, the cover being a substantially rigid cover and configured to close off an opening to a void having a side wall, and the cover defining a pair of opposed sides (20, 22), being an operatively top side and an opposed underside; and a locking assembly for the cover, the locking assembly comprising: a mounting arrangement mounted to the underside of the cover; a link pivotally connected to the mounting arrangement, the link defining a first end and a second, free end; a locking member carried by the second, free end of the link, the locking member being configured to frictionally engage with the side wall of the void in a locking position, in use, wherein such frictional engagement of the locking member with the side wall of the void in the locking position, in use, locks the cover; an actuating member connected to the link and accessible via the operatively top side of the cover, the actuating member being operable to displace the link relative to the mounting arrangement to cause the locking member to frictionally disengage from the side wall of the void to a disengaged position, characterized in that the actuating member is at least pivotally connected to the link. a mounting arrangement mounted to the underside of the cover; a link pivotally connected to the mounting arrangement, the link defining a first end and a second, free end; a locking member carried by the second, free end of the link, the locking member being configured to frictionally engage with the side wall of the void in a locking position, in use, wherein such frictional engagement of the locking member with the side wall of the void in the locking position, in use, locks the cover; an actuating member connected to the link and accessible via the operatively top side of the cover, the actuating member being operable to displace the link relative to the mounting arrangement to cause the locking member to frictionally disengage from the side wall of the void to a disengaged position, characterized in that the actuating member is at least pivotally connected to the link.