A mooring post unit is provided with a cable holding device on top of the mooring post. The cable holding device has a first pulley wheel, a second pulley wheel and a cable clamp, arranged to guide a mooring cable from a ship over the first pulley wheel to the clamp, back and forth via the second pulley wheel. A hydraulic force limiter is coupled between the second pulley wheel and the mooring post. The hydraulic force is expandable and compressible in the direction of a force exerted by the axis of the pulley wheel. The hydraulic force limiter temporarily gives way when a peak in the force exceeds a threshold. The clamp comprises a pair of drums, around which the mooring cable runs back and forth. By synchronously rotating the drums, the mooring cable may be hauled in or paid out under stress.