Recording of a radio exchange between Iran and the British warship moments before a British tanker was seized by Iranian armed force revealed details about the confrontation in the Persian Gulf.
The audio obtained by maritime security firm Dryad Global revealed that the Royal Marine's 'HMS Montrose' was approached by Iranian Revolutionary Guard who said that the Stena Impero needed an inspection for "security reasons."
Iranian vessel told the fright vessel, thought to be Stena Impero, to change its course, saying, "If you obey you will be safe."
HMS Montrose the told Stena Impero, "As you are conducting transit passage in a recognised international strait, under international law your passage must not be impaired, impeded, obstructed or hampered."
The Iranian tanker was then warned by the frigate to not "violate international law" by attempting to board the tanker.
The British flagged-oil tanker was seized by Iranian authorities on Friday. The tanker was captured after it collided with a fishing boat and failed to respond to the smaller vessel, reported Iran's state agency.
The tanker had 23 crew members of Indian, Russian, Latvian and Filipino nationals abroad.
On Sunday, Director-General of Ports and Maritime Organisation (PMO) Allahmorad Afifipour said, "All 23 crew members aboard the ship are safe and in good health in Bandar Abbas port."
On the same day the tanker was seized, it is reported that a British-owned Liberian-flagged tanker MV Mesdar was boarded by armed guards but was eventually released.
Britain's Defence Minister Tobias Ellwood said that sanctions against Iran were being considered as counter-measures if the seized tanker is not released.
Foreign Minister Jeremy Hunt termed the seizure as "illegal" and said the situation "raises very serious questions" about the security of British and international shipping in the Strait of Hormuz.
Hunt also revealed, following a phone conversation with Iranian counterpart, that Iran considers the seizure as "tit-for-tat situation" following the detention of an Iranian tanker in Gibraltar earlier this month.
The 'Grace 1' Iranian tanker was seized by Britain earlier this month because of suspicion that Iran violated EU sanctions and was carrying oil to Syria.
The Grace 1 seizure was called as legal detainment in Gibraltarian waters "totally within the law" according to Hunt. Iran described the incident as "piracy".
"Our priority continues to be to find a way to de-escalate the situation," Hunt said.
