Cylinder lock and associated turning flat key

A cylinder lock with a flat key (1) for insertion into the key channel (14) of the cylinder lock, into which key channel (14) tumbler pins and at least one supplementary tumbler pin (9) project and the supplementary tumbler pin (9) when the key (1) is fully inserted is displaceable into a release position by a lifting flank (8') of a two-armed pivoted lever (4). The pivoted lever (4) is disposed in an opening (24) of the key bit (3) and is capable of swivelling about an axis extending at right angles to the insertion direction, the swivelling of the pivoted lever (4) being effected by the action of a control flank (7') of the pivoted lever (4) upon a cam (13, 18'). The lifting flank (8') and the control flank (7') are associated with different arms (7, 8) and tumbler pin (9) and cam (13, 18') are associated with the same key channel wall (14').