The Swordfish Mark III carried a large centimetric radar installation beneath the aircraft. That installation prevented it from carrying the normal torpedo load. The trade was acceptable because the type's later role emphasized anti-submarine patrol, where finding a surfaced boat mattered more than retaining its original anti-ship weapon. The change shows an old airframe being adapted around a more valuable sensor and a narrower wartime mission.
Notable Point · 57:57-58:11
Why the Swordfish Mark III traded its torpedo for radar
The Swordfish Mark III's large centimetric radar installation displaced its torpedo, an acceptable trade once anti-submarine patrol had become the aircraft's main job.