United States. An Iranian Foreign Ministry official called the seizure "piracy," stating that the UK does not have the right to implement sanctions against other nations "in an extraterritorial manner". On 10 July 2019, tensions were raised further when boats belonging to Iran's Islamic Revolutionary Guard Corps approached a British Petroleum tanker, British Heritage, impeding it while it was transiting the Strait of Hormuz. The Royal Navy frigate positioned themselves between the boats and ship so that it could continue its journey. On 14 July 2019, British Foreign Secretary Jeremy Hunt said Grace 1 could be released if the UK received guarantees the oil — 2.1 million barrels worth — would not go to Syria. On 19 July 2019, Iran media reported that the Swedish owned but British-flagged oil tanker Stena Impero had been seized by the Iranian Revolutionary Guard in the Strait of Hormuz. A first tanker, MV Mesdar, which was a Liberian-flagged vessel managed in the UK, jointly Algerian and Japanese owned, was boarded but later released. Iran stated that the British-flagged ship had collided with and damaged an Iranian vessel, and had ignored warnings by Iranian authorities. During the incident HMS Montrose was stationed too far away to offer timely assistance; when the Type 23 frigate arrived it was ten minutes too late. HMS Montrose was slated to be replaced by , however in light of events it was decided that both ships would subsequently be deployed together. On 15 August 2019 Gibraltar released Grace 1 after stating that it had received assurances she would not go to Syria. The Iranian government later stated that it had issued no assurances that the oil would not be delivered to Syria and reasserted its intention to continue supplying oil to the Arab nation. On 26 August, Iranian government spokesman Ali Rabiei announced that the 2.1 million barrels of crude had been sold to an unnamed buyer, in either Kalamata, Greece or Mersin, Turkey. A US court issued a warrant of seizure against the tanker because it was convinced that the tanker was owned by the IRGC, which is deemed by Washington a foreign terrorist organization. On 15 August 2019 the UK's new Boris Johnson-led government agreed to join the U.S. in its Persian Gulf maritime security Operation Sentinel, abandoning the idea of a European-led naval protection force. On 4 September 2019 Iran released seven of the 23 crew members