Abstract: A locking manhole cover and key combination of the present invention is in the form of a manhole cover having a lock on its undersurface and a vent hole through the manhole cover. The lock comprises a plurality of locking bars spring biased to a locking position, a rotatable actuator accessible through the vent hole for moving the locking bars to an unlocking position with the key being fittable through the vent hole to operate the actuator. The key itself includes a first shaft portion turnable in the vent hole for rotating the acutator and pulling the locking bars to the unlocking position and a second shaft portion which when located in the vent hole prevents rotation of the actuator and holds the spring biased locking bars away from the locking position.