"I'm sorry, but the timne to confront them was when the whole thing started. HMS Cornwall could have, should have stopped it then!"
Spot on, as they say! The Commander of the Cornwall, had the power to respond, and he is most assuredley kicking himself for making the phone call instead of keeping his eye on the ball. There is a time for action, and you can't get it back. He could have called about 30 min later and said " Sorry sir, I had to act to protect our troops, and those Iranies won't be bothering us again." Even if fired, he would have held high respect in his retirement.
I suspect that they had been given strict instructions not to fire on Iranians without contacting HQ first.