(57) A locking device, particularly suitable for use in the lid or door of a safe, comprises a first locking mechanism which extends and retracts bolts, and a second locking mechanism which acts to lock the first locking mechanism. The second locking mechanism is actuable in stages by sequence of key operations in an externally accessible lock. For extra protection an obstruction may be included which requires a further operation to be carried out simultaneously with one of the key operations. In one embodiment the first locking mechanism comprises a set of bolts which each carry a toothed gear wheel, and a central gear wheel which meshes therewith. The second locking mechanism comprises a blind gear mounted co-axially with the central gear wheel and means for moving the gears along the axis to select the central or blind gear to open or lock the first locking mechanism.