Lock cylinder that can be unlocked by an authorised key, this cylinder comprising : - a stator , - a rotor (52; 110) which is mounted in the stator so as to be rotatable about a longitudinal axis and which has a tubular armature in which a key channel is formed which extends along the longitudinal axis and into which the authorised key can be introduced in order to drive the rotor in rotation about its longitudinal axis - an electric actuator , - a locking lever movable, by the electric actuator, between a locking position in which it prevents unlocking of the cylinder and an unlocking position in which it allows unlocking of the cylinder, - a blocking member movable between : - a retracted position in which it releases the rotation of the rotor by the key, - a firm locking position in which it blocks the rotation of the rotor and systematically prevents the movement of the locking lever to its unlocked position, and - an intermediate blocking position in which it blocks the rotation of the rotor and allows the locking lever to move to its unlocked position, characterised in that the rotor (52; 110) has a shaft (62; 112) which is mounted in the interior of the tubular fitting in the extension of the key channel and is displaceable parallel to the longitudinal axis, this rod having a stop which projects into the interior of the key channel and comes to bear on the end of the key inserted into the key channel so that the rod is displaced by the key, which protrudes into the key channel and abuts the end of the key inserted into the key channel so that the rod is moved by the key, relative to the fitting, from a rest position to a depressed position, said rod being shaped to move the locking member from its firm locking position to its intermediate locking position when the rod moves from its rest position to its depressed position. - a stator , - a rotor (52; 110) which is mounted in the stator so as to be rotatable about a longitudinal axis and which has a tubular armature in which a key channel is formed which extends along the longitudinal axis and into which the authorised key can be introduced in order to drive the rotor in rotation about its longitudinal axis - an electric actuator , - a locking lever movable, by the electric actuator, between a locking position in which it prevents unlocking of the cylinder and an unlocking position in which it allows unlocking of the cylinder, - a blocking member movable between : - a retracted position in which it releases the rotation of the rotor by the key, - a firm locking position in which it blocks the rotation of the rotor and systematically prevents the movement of the locking lever to its unlocked position, and - an intermediate blocking position in which it blocks the rotation of the rotor and allows the locking lever to move to its unlocked position, - a retracted position in which it releases the rotation of the rotor by the key, - a firm locking position in which it blocks the rotation of the rotor and systematically prevents the movement of the locking lever to its unlocked position, and - an intermediate blocking position in which it blocks the rotation of the rotor and allows the locking lever to move to its unlocked position, <EOS>