Daily Star Online understands HMS Montrose – a Type 23 frigate – was on duty today as she guarded British shipping passing through the Strait of Hormuz. It is believed she escorted oil tanker Pacific Voyager as she sailed through the piece of sea that separates the United Arab Emirates from Iran. The waterway has been the scene of attacks of tankers this year amid a renewed flaring of tensions in the Gulf. Britain has been roped into the feud as the Royal Marines stopped a tanker at Gibraltar which is believed to have transporting Iranian oil to Syria.  Iran reacted furiously and outright threatened to board British ships – warning UK officials to “be scared”.   Royal Navy warship HMS Montrose – who is stationed in Bahrain – was on alert in the Strait of Hormuz this morning as Pacific Voyager passed Iran. The tanker had to be checked on by UK officials over the weekend as she stopped close to Iranian waters – sparking fears she had been boarded. Weighing 4,900 tons, the HMS Montrose carries a Wildcat helicopter and is bristling with weapons. She has a 4.5inch gun on her bow and carries the powerful Sea Ceptor anti-air missiles.  In a statement, the Ministry of Defence said: “The UK maintains a long standing maritime presence in the Gulf. "We are continuously monitoring the security situation there and are committed to maintaining freedom of navigation in accordance with international law.”      Iran has been squaring up to the West as it reels over the scrapping of the so-called nuclear deal by the US, which traded a pledge not to develop nukes for eased sanctions. The ayatollah has been demanding that nations such as Britain and its European allies pick-up the slack as Donald Trump’s administration imposes crushing new penalties. Britain however infuriated Iran last week when the Royal Marines seized the Grace 1 supertanker as she entered the Mediterranean. Commandos took the vessel without a shot being fired as it is suspected of breaching EU sanctions on the brutal Syrian regime of Bashar al-Assad.    Iran responded by threatening to seize British ships in retaliation amid fears of a new tanker war in the Gulf.  Five oil tankers and a cargo ship have been attacked in the Gulf in the past two months. Tehran denies any involvement in the attacks, but they have been blamed by the US.  And in an escalation, Iran shot down a US drone – nearly prompting a limited strike by Washington before an 11th hour U-turn by Trump.    Iran has since broken its nuclear agreement by stepping up its enrichment of uranium. Tehran has said the measures are just for power plant fuel, and will not be used for the development of nukes. The foreign ministers of Britain, France and Germany, plus the foreign affairs chief of the European Union, said in a statement that Iran was "pursuing activities inconsistent with its commitments”. Trump’s administration argues the deal was too soft on Iran and it didn’t impact its missile programme of sponsor of terrorism.