1 2 ▁September ▁ 1 9 4 1 , ▁last ed ▁ 2 5 ▁days . ▁She ▁then ▁returned ▁to ▁K iel . ▁▁ 3 rd ▁and ▁ 4 th ▁pat rol s ▁Starting ▁from ▁K iel ▁on ▁ 2 5 ▁November ▁ 1 9 4 1 , ▁she ▁sa iled ▁to ▁Lor ient ▁in ▁occupied ▁France , ▁arriv ing ▁on ▁ 1 2 ▁December . ▁ ▁Her ▁fourth ▁and ▁final ▁sortie ▁began ▁on ▁ 1 5 ▁December ▁ 1 9 4 1 , ▁taking ▁her ▁from ▁Lor ient , ▁through ▁the ▁Bay ▁of ▁B isc ay ▁to ▁a ▁point ▁in ▁mid - At l antic ▁north ▁of ▁the ▁Az ores . ▁She ▁then ▁turned ▁toward ▁the ▁Mediter rane an . ▁ ▁L oss ▁She ▁was ▁s unk ▁off ▁Tang ier , ▁Mor oc co , ▁on ▁the ▁night ▁of ▁ 2 1 ▁December ▁ 1 9 4 1 ▁by ▁a ▁F aire y ▁S word fish ▁M k . ▁I , ▁V 4 4 3 1 , ▁flying ▁with ▁ 8 1 2 ▁Naval ▁Air ▁Squadron ▁from ▁R N AS ▁North ▁Front , ▁Gib ral tar . ▁U - 4 5 1 ▁was ▁first ▁detected ▁by ▁Air - to - Sur face ▁V essel ▁rad ar ▁( AS V ) ▁at ▁a ▁range ▁of ▁ 3 - 1 / 2 ▁miles ▁and ▁about ▁ 1 8 ▁miles ▁N W ▁of ▁Cape ▁Spart el . ▁" The ▁S word fish ▁closed ▁the ▁contact ▁and ▁sight ed ▁the ▁U - Bo at ▁on ▁the