US President Donald Trump says the U.S. Navy will begin a blockade to stop ships from entering or leaving the Strait of Hormuz.

Iran wants to collect tolls from vessels travelling through the strait, but Mr Trump says no one who pays them will “have safe passage on the high seas”.

• Guest: Professor Rockford Weitz, director of the Maritime Studies Programme at Tufts University's Fletcher School
• Producers: Oscar Coleman and Eleni Psaltis