A removable core lock and key device comprises a cylinder housing (10) and a cylinder core (20), which is accommodated in a circular opening in the cylinder housing. A plurality of pin tumblers (22) are movable under influence from code surfaces of a key, wherein at least part of the pin tumblers are provided in a recess (20b) in the mantle surface of the cylinder core. A cam adapter (40) is rotatably provided in the opening in the cylinder housing. The cam adapter comprises an engagement portion (40c) which engages the recess (20b) in the mantle surface of the cylinder core when the cylinder core is in an operative position, wherein at least one of the pin tumblers is movable between a blocking position, in which the engagement portion of the cam adapter cooperates with the at least one pin tumbler to prevent mutual axial movement of the cam adapter and the cylinder core, and a release position, in which mutual axial movement between the cam adapter and the cylinder core is allowed.