HMS Montrose escorts two ships through Strait of Hormuz (Picture: Royal Navy).
The commanding officer of HMS Montrose says the vessel has escorted British ships safely through the Strait of Hormuz more than 20 times in the past month.
It comes after the Government told the Royal Navy to escort tankers through the narrow passage that hugs the coast of Iran.
HMS Montrose has been operating in this way in response to the seizure of the Stena Impero, a British flagged oil tanker, earlier this month.
Iranian forces boarded and captured the ship, and her 23 crew members are still being held.
Iran claims the ship was "violating international shipping rules".
However, many believe it was a reaction to the seizure and impounding of an Iranian oil tanker by Gibraltar, which was thought to be attempting to smuggle oil illicitly to Syria – against international sanctions.
Speaking on BBC Radio 4, Commander William King, Commanding Officer, HMS Montrose, said: "I've had 85 interactions with Iranian forces.
"They'll claim that perhaps our presence is illegitimate, even though we're completely lawfully in international waters.
"They may also run boats in at speed towards us to test what warning levels we get to, and obviously for the merchant shipping they're not used to seeing that and as such our presence is key to reassuring them."
Royal Navy ships have clearly defined operating procedures to deal with an encroaching unfriendly ship.
Radio messages, deviation of route and even warning shots can all be employed, with the use of force a last resort deterrent.
HMS Montrose will continue to patrol until the end of August, when she will enter a period of maintenance.
But the Type 45-destroyer HMS Duncan has recently joined her in the Gulf, to continue to support British-flagged shipping.
The UK has several other assets in the region, including minehunters and Royal Fleet Auxiliary vessels.
Commodore Duncan Lamb, Head of Royal Fleet Auxiliary, said: "We've got RFA Cardigan Bay in the Gulf at the moment, specifically conducting support to the minesweeping effort out there.
"We've got an RFA tanker which is on its way out to the Gulf and of course HMS Duncan is joining the group as well.
"So we've got a significant presence in the Gulf at the moment."
For now, HMS Montrose and her 200-plus crew continue their patrol, while diplomatic efforts work to find a solution.