Why did the British let their sailors be taken by Iran without firing a shot?

Question

The British Navy is armed. They were boarding and inspecting ships in a warzone during a time of war. They were (hopefully!) prepared for any kind of trouble, why inspect ships outside of BRITISH waters otherwise? Why did they let their sailors be taken without a whimper?!

Answer 1

The 15 sailors were armed with hand guns while the Iranian Coast Guard was armed with automatic weapons. It would have been a massacre.