A lock system, lock and key is provided. The lock includes additional cutouts on the face plate (123), requiring the insertion of a corresponding unblocking member on the keyblade (144). The unblocking portion engages an engagement portion (162) to allow release of a corresponding sidebar (126), thereby allowing rotation of the lock. The engagement portion (162) additionally must project to the correct length to allow the engagement portion (162) to travel the correct distance to release the sidebar (126).