What game is Iran playing?

It is almost impossible to fathom what the leaders in Tehran are up to. They are deliberatey trying to provoke the US, UK and others with shipping interests in the Gulf waterway by seizing or blowing up oil tankers but to what end? Do they imagine that the West will just cave in and say "OK you win we'll do your bidding, what do you want?" The trouble is they have probably calculated without much difficulty that no one wants a war, so they can get away with doing exactly as they please. But, again, for what purpose? The latest seizure by the Iranian Revolutionary Guards naval branch of two British tankers in the Gulf (one later released) is as about as provocative as you can get. But what are the UK Government and the Royal Navy going to do about it? There's only one frigate out there at present, HMS Montrose, although there are two other Royal Navy warships on the way. But HMS Montrose was absent when the two tankers were seized. As a British admiral once famously said, "A warship cannot be in two places at once." So HMS Montrose was off somewhere else at the time. That was clever planning by the Iranian Revolutionary Guard and embarrassing for the Royal Navy. The UK Government has sent a strong warning to Iran but Great Britain no longer rules the waves. It will take a tough and determined government to see off the Iranians and that includes ordering warships to fire their guns if these Iranian fast boats come within spitting distance. Britain currently has a prime minister a few days away from stepping down and a new prime minister waiting in the wings, whether Boris Johnson or Jeremy Hunt. Neither will want to start their premiership with a war. Tehran has thought that out obviously. But if Tehran wants the UK to help salvage the 2015 nuclear deal, what on earth are they doing targeting British oil tankers? Was it just in retaliation for the seizure by the Royal Marines of an Iranian oil tanker illegally shipping oil to Syria in breach of international sanctions? I guess it could be as simple as that. So what can the UK do next? Basically the 2015 nuclear deal, still held together by Russia, China, the UK, France and Germany, is dead in the water. If ever there was a time for Nato allies to remain cohesive and strong it is now, never mind what Russia and China do. And that means, however much they hate Donald Trump's decision to withdraw the US from the 2015 deal, the UK, France and Germany need to be steadfast against Iran and join the US in withdrawing from the agreement and adopting a united stand against Tehran. Only then will Iran stop baiting and provoking the West.