A locking apparatus for a hydromechanical spring energy store drive for actuating a medium-voltage or high-voltage circuit breaker is disclosed, the spring energy store drive includes a working piston, which is guided in an axial cutout in a pressure housing or working cylinder, and a spring energy store arrangement. The locking apparatus includes a first pressure region and a second pressure region, which are under elevated pressure when the circuit breaker is closed, and a third pressure region, which is unpressurized. The latching bolt can be arranged perpendicular to the working piston, via a latching apparatus, which can be arranged on a side of the latching bolt, which is to point towards the working piston and via the spring energy store arrangement, which is to be pushed away from the working piston.