The first commission of Onyx saw her visit Swansea in South Wales for the investiture of His Royal Highness The Prince of Wales.
Postwar, Onyx sank the hulk of the landing ship Sir Galahad with a Mk 8 Torpedo after firing two Mk 24 Tigerfish, the second Tigerfish, after a ten minute delay, at the hulk; both failed to explode [REF] probably due to torpedo battery faults.