US blockade of Iranian ports takes effect

An American blockade of the Strait of Hormuz has come into force, after the failure of peace talks with Iran at the weekend. Tehran says it'll retaliate, but President Trump has repeated his threat to destroy any Iranian attack vessels which approach the blockade. We speak to a representative of independent tanker owners and operators across the globe .
Also on the programme: The dispute between President Trump and Pope Leo deepens, with Mr Trump saying he would not apologise to the pontiff; and we hear about the life of a self-taught topiary artist who has been called the "Picasso of Plants".