As a postscript, look at the Type 42 Batch 1 full cut thread, for more details. The Ikara handling system was a tight fit around a 12 75 inch torpedo. It couldn't accommodate the fatter 16.5 inch diameter bomb armed versuon. The only place this round could be handled/inserted was the IAR loading trolley which then fed the launcher directly. I.e a nuclear round thus blocked loading of conventipal rounds, until fired, or removed from the IAR.