Lemurian;
As a matter of fact, until we see the other side of the fin, evidence points towards a longitudinal breakage : the base of the rudder is broken, hinting at possible compression stresses,
Possibly in the chaos the trailing edge of the rudder met with the trailing edge of the HS or some other detached part.
Where are the rudder actuators attached to the rudder? Perhaps that section of the rudder was ripped off.