Iran just blew up another tanker in the Strait of Hormuz

So why does one tanker fire matter so much?

Because of where it happened.

The Strait of Hormuz carries close to a fifth of the world's oil. And it has barely been working for months.

It's been effectively shut to normal shipping since the end of February. On 4 October, only four ships made it through. Before all this started, it was 85 ships a day.

And the ships still trying it are paying for it. War-risk insurance for one supertanker trip through the strait is now up to $10 million. That's about 30 times what it cost before the crisis.

Here's the thing though. This is not new.

Iran's Revolutionary Guards have been saying tankers hit mines in this strait since at least June. They've even named vessels before, back in September. And in the nine days before this one, nine ships were hit in or near the strait, most of them carrying crude oil.

So this fits a pattern. It isn't a new kind of attack.

The Guards keep warning ships to stick to routes Iran has approved, or face punishment. A tanker was hit in the strait the day before this one. An LPG tanker was separately reported hit on the same day.

Brent crude is trading at $104.72 a barrel right now.

So here's the real question. Is Iran enforcing a blockade on ships that break its rules? Or is this just uncontrolled damage to a waterway the whole world still needs?

Nobody outside Iran has said which.