Memo to the Brits: The war has already started.
lol!
Having your people held hostage will start trouble a whole lot faster. The Brits will have to bow and scrape to get their people back.
Not to mention the fact that the Iranians had dome this to them before.
If the Brits were unwilling to defend their personnel, those sailors and Marines should never have been sent out. That was their fist mistake.
And note to whichever Brit was running things out there on the waterway that day: Asking for permission was your second mistake.