Hi Brian,

You can get some info on GRAZ in [www.feldgrau.com]
HMS UNRIVALLED did not carry out any attack on 1.12.1942 so she could not have sunk CITTÀ DI TRAPANI.
Your point of Meditarrenean eels (or dolphins) is well taken but at the same time one cannot dismiss the possibility of an Italian submarine: this was on the Cagliari-Naples route and quite a few Italian submarines went back and forth between these two bases. Following the Allied landings in Africa, the German Naval Liaison had stressed that Italian submarines should use more salvo firing as it was not a time to save torpedoes. Certainly a submarine operating near Bone or Algiers would probably have refrained from firing a full salvo at another submarine since it might expect more lucrative targets but a submarine on passage between Cagliari and Naples might not have the same inhibition.
Another outside possibility is that RORQUAL was attacked by the submarine P.222 which was reported sunk by FORTUNALE off Capri on the same day. If P.222 was not the submarine sunk (as far as I know no evidence was recovered) she may have been on her way back to Algiers and mistakenly attacked RORQUAL. And British submarines did fire full salvoes at enemy submarines. A bit far-fetched but who knows?

Best regards,

Platon