Locking system with additional blocking by formations and counter-formations on key and lock at transverse or oblique angle to insertion direction of key

A locking system is set forth having a key and a lock cylinder. The lock cylinder has a cylinder core journalled in a housing and having a keyway for inserting the key. A plurality of tumblers actuable by the key and an additional blocking formation movably arranged in a guide passage of the cylinder core project into the keyway, said additional blocking formation being displaceable obliquely or transversely to the direction of insertion of the key. The additional blocking formation is made for cooperation with a counter-formation arranged at the key blade with a key introduced up to the maximum insertion depth. The counter-formation is in this respect arranged in a groove or recess starting from the key tip and extending in the longitudinal direction of the key blade.