The US-Iran war has reached a new front, after a U.S. strike hit an Iranian warship in the Indian Ocean off ​Sri Lanka, deepening a crisis that has paralysed shipping through the Strait of Hormuz for a fifth day and choking off vital Middle East oil and gas flows.

Iran has warned vessels not to pass through the crucial waterway in the south of the country effectively halting a fifth of the world's energy supply transit.

US President Donald Trump is now offering insurance guarantees and naval escorts to protect, as he says, the "free flow of energy to the world".

• GUEST: Dr Neil Quilliam, energy policy, geopolitics and foreign affairs specialist at Chatham House and the Energy Research Director at SRMG Think
• PRODUCER: Brooke Young, Eddy Diamond