BBC Radio 4: The Iranian threat to shipping in the Strait of Hormuz

The smaller vessels, the locally operated fast attack craft and so on, are very often operated by the Islamic Revolutionary Guard Corps so a very different chain of command to the traditional navy and operating through a different remit and a different line. So they may well be operating in small pockets, small cells and operating within a strategy that they are aware of and they know of but it may not be very closely controlled from Tehran. And what threat do they pose to shipping? Can they be ignored? They certainly can't be ignored. They are difficult to detect, difficult to engage with, and there can be a lot of them"