The Royal Navy's HMS Duncan has arrived in the Gulf to protect British-flagged ships travelling through the Strait of Hormuz amid rising tensions with Iran.
The Type 45 destroyer will work alongside HMS Montrose until she docks for routine maintenance in late August.
Earlier this week, it was confirmed that the Royal Navy had been tasked with escorting British ships sailing through the Strait of Hormuz following the seizure of one ship by Iran.
The newly-appointed Defence Secretary Ben Wallace said: "Freedom of Navigation in the Strait of Hormuz is vital not just to the UK, but also our international partners and allies.
"Merchant ships must be free to travel lawfully and trade safely, anywhere in the world.
"I’m pleased that HMS Duncan will continue HMS Montrose's fine work in helping to secure this essential route.
“While we continue to push for a diplomatic resolution that will make this possible again without military accompaniment, the Royal Navy will continue to provide a safeguard for UK vessels until this is the reality.”
According to the Ministry of Defence (MOD), HMS Montrose has so far accompanied 35 British ships through the Strait on 20 separate transits - travelling more than 6,000 nautical miles.
The ship has been covering an operating area of 19,000 nautical miles, the MOD added.
The UK is to send two more ships to the region later this year.
Type 23 frigate HMS Kent will take over from HMS Duncan, supported by RFA Wave Knight.
HMS Montrose, also a Type 23 frigate, will remain stationed in the Middle East until 2022.
The MOD has stressed the latest deployments are not in response to increased tensions with Iran.
The deployments are part of Operation Kipion - the operational name given to operational name for British forces in the Gulf and the Indian Ocean.