Abstract: A key operated cylinder lock is disclosed, including a hollow stationary cylinder housing enclosing a turnable power transmission element and a locking bar having a position locking the turning movement of said power transmission element relative to said cylinder housing. The cylinder lock further includes a set of discs including a number of locking discs turnable by means of combination surfaces on a key of said lock, the locking discs being turnable, by the turning movement of said key, from an initial key insertion position to a releasing position, in which the power transmission element is released from its locked connection to the cylinder housing, whereby the key of the lock is arranged to directly transmit a turning force to a number of locking discs only in a direction from said initial position to said releasing position.