Locking system

A locking system having a key and a lock cylinder which has a cylinder core which is journalled in a housing and has a keyway for the introduction of the key, wherein a plurality of tumblers actuable by the key and an additional blocking element movably arranged in a guide passage of the cylinder core and displaceable obliquely or transversely to the direction of insertion of the key projects into the keyway, wherein the additional blocking element is made to cooperate with a counter-element arranged at the key blade with the key introduced up to a maximum insertion depth, wherein the counter-element is completely arranged in a groove or recess extending in the longitudinal direction of the key blade and starting from the key tip, and wherein a guide element arranged in the cylinder core forms the guide passage for guiding the additional blocking element and projects into the keyway such that the guide element forms an abutment element at the lock cylinder side which defines the maximum insertion depth of the key into the keyway, said abutment element at the lock cylinder side being for an abutment at the key side which is formed by the end region of the groove or of the recess remote from the key tip.